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Old 02-19-2012, 10:11 AM   #41
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T5HO lamps and Reflectors

T5HO lamps are inherently superior to CFLs. They spread the light out more evenly than CFLs, and they can be placed closer to the screen without overpowering the algae. Notice in this picture below how use of T5HO can result in almost perfectly even light coverage:

With that factor alone, bare T5HO lamps likely fall in between bare CFL and properly reflected CFL as far as scrubbing power is concerned.

Reflected T5HO is very arguably superior to all other fluorescent lighting. However, it is more difficult to build a T5HO Algae Scrubber. You have basically 2 options.

The first is to buy and build around a stock fixture, like the Nova Extreme 1126/1127. This fixture was great because it had individual reflectors and only cost about $70 shipped, but not so great because the endcaps were cheap and would bust in shipping. However, this fixture has reportedly been discontinued. You can still find it, but for how much longer, who knows. The only other fixture that is decent that I have found is the Aquatic Life 2x24 T5HO fixture, which runs around $100.

The second is to build something upon which to mount and protect endcaps, then connect to a ballast. Also, since the reflectors are generally one of the more expensive components, enclosing the screen in an acrylic or glass box to protect them is pretty much a given.

As far as lamps go, the same rules apply. I personally use the PlantMax 3000K Red/Bloom lamp, I can get them for $5 each in packs of 8 (up from $4/ea). Here’s my Algae Scrubber, Revision #2 (which will soon be replaced with and LED Algae Scrubber)

With a custom build, you can really use all the power of a T5HO lamp. The TEK-II reflectors from Sunlight Supply are expensive, but I have had great results. Other individual-lamp reflectors, such as Ice Caps, work very well. Stock fixtures work best when each light has an individual reflector, but just about any reflector will do better than none.

The ballast you use can also make a big difference. I recently learned that Workhorse ballasts are not that great, and that you can get a lot more out of your lamps by switching to an Ice Cap ballast. Get the right one though, or you can over-drive the lamps and quite literally cause them to explode. Not good for da reef mon.

Sunlight Supply also makes a T5HO fixture that needs no external ballast, and you can daisy-chain up to 10 of them together. However, the reflector they make for it is just plain aluminum and nowhere near as reflective as the TEK-IIs or Ice Caps, which use Anolux-MIRO IV (which is something like 96% reflective)

The disadvantage to T5HO is that you’re pretty much locked into a dimension that you have to build around. T5HO lamps come in standard lengths of 24”, 36”, 48”, and 72”. There are shorter lamps, such as 18”, but it’s difficult to find lamps in the right color temperature, and they’re generally much more expensive than 24” or 48” lamps (which are the cheapest T5HO sizes). This means that the dimensions of your Algae Scrubber are locked into about 20-22” in length, which is the illuminated length of the lamp (the fixture is 24”, the lamp right around 21” long). This means your flow to the screen has to be around 700-800 GPH. You can make the screen narrower, but you will end up wasting part of the lamp. The benefits of T5HO over CFL would outweigh this loss to a certain point though.

This can be overcome if you have a dedicated fish room, or enough space to make a vertical T5HO Algae Scrubber, like this:

And to my knowledge, those endcaps are no longer available. Right now, is seems many companies are shifting away from T5HO and putting all their efforts into LED development. So, it’s time to roll with the punches – and they’re feather punches, as you’re about to see…

My tanks: 120 Reef w/L2 Algae Scrubber, 60 Reef Pond w/floating Algae Scrubber, 40 Breeder Reef w/L2 UAS Tester Algae Scrubber
I maintain: 144 SW Reef w/L2 Algae Scrubber | 200 SW Reef w/L4 Algae Scrubber
Special knowledge: Algae Scrubbers, Acrylic Fabrication
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Old 02-19-2012, 10:12 AM   #42
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LEDs – Why they are different

LEDs are a completely different source of light. Fluorescent, metal halide, HPS, and other HID lighting are all mercury based, and the light is shifted from the ultraviolet range into the visible range with phosphors. LEDs emit certain colors of light depending on the compounds used in the diode itself, so it is initially visible light; phosphors are then sometimes used to shift wavelength to achieve various colors.

LEDs, very recently, have proven to be highly efficient, and as more people build LED Algae Scrubbers, more information is being confirmed. There are still a few unanswered questions, but LED Algae Scrubbers so far have been shown to have a few major advantages over CFL and T5HO.

The most obvious one is lamp life - they never actually burn out (unless you drive them too hard). LEDs have what is called an L70 (or L80) rating, which is the number of hours, running at rated junction temperature, at which the total lumen output will have dropped to 70% of its original output. At this point in time, that is usually about 50,000 hours. If they are on 18 hours/day, that's about 7.6 years to L70.

However, as has been predicted, there is a big difference with LEDs when it comes to Algae Scrubbers. Since LED Algae Scrubbers ‘waste’ very little (if any) bandwidth, they are, in effect, double or better the intensity of CFL or T5HO for comparable PAR output. What this means is that you generally only need to run them half as long, or 9 hours a day (just like the double-light CFL/T5HO Algae Scrubber). Couple that with the fact that the intensity of a well built LED Algae Scrubber fixture is, on average, 1.5x the PAR of a comparable T5HO fixture (I have verified this on a Nova 1126/7 vs 50W e-Shine), LEDs are somewhere between 3 and 5 times as effective. Some DIY LED users have claimed that they have found that you can get away with 1/5 the total LEDs wattage vs. CFL or T5HO and get [i]better results[i/]. Not only that, 50,000 hours at 9 hours/day is over 15 years to the L70 date. Some manufacturers are claiming L70 dates into the 100,000 hour range, and while that may not be proven, it’s actually highly probable the LEDs themselves will last that long (the rest of the fixture? I doubt it.)

Some possible negative factors for LEDs are the up-front initial cost, long-term phase shift, and the effect of steadily decreasing output. Phase shift is the reason that most small municipal airports are avoiding LED lighting; white LEDs are actually blue with phosphors added, and they ‘fade’ over time, and shift to blue. Runway lights are white, taxiway lights are blue, and getting them confused is bad. The LED industry is rapidly evolving, so the L70 numbers will continue to increase, cost will decrease, and issues like phase shifting will likely be improved upon. The flipside to the L70 and phase shift issues is that most people who are DIYing LED Algae Scrubber lighting will likely replace their fixture with the next best thing before this ever becomes an issue, if it even becomes an issue at all. With a stock fixture, at least those currently available at an affordable price, will probably fail for some other issue before the LEDs go bad (driver, power supply, fan, moisture problem, etc), prompting the user to replace the fixture with a better one.

LED Grow Lights for Algae Scrubbers

The LEDs that you want to use for growing algae on an Algae Scrubber are the exact fixtures that are used to grow plants. There are different plant-growth fixtures available, and some are not what you want. ‘Flowering’ lamps have a lot of variety of lamp types that you do not need.

Here’s the bottom line: you only need RED. Nothing else is really necessary. White LEDs of any kind have not proven to be highly effective, and neither are Blues (with the exception that they accompany reds in a low ratio).

The best results so far have utilized 660nm “Deep Red” LEDs; there have been far fewer attempts using 630nm Red LEDs. These wavelengths roughly correspond with the Chlorophyll A and B red peaks. Optionally, some 455nm Royal Blue LEDs can be thrown in; according to horticulturalists, and one study by NASA, this ratio is approximately 7:1 red: blue.

One Algae Scrubber user, who has made multiple LED Algae Scrubbers over the past couple years, commented that the use of only 660nm produced great growth, but with the addition of a single blue LED, that growth got ‘stronger’. The algae was more difficult to scrape from the screen, and the strands were more stringy or ribbon-like, and less hair-like. This anecdotal evidence suggests that the blue component is used supplementally in some fashion. So a little blue can’t hurt; add too many and you’re probably just wasting power.

To my knowledge, no one has tried 660s in combination with 435s (which are the corresponding “A” peaks) or 630s with 455s (“B” peaks); however I have a couple of fixtures that I had custom made just for the purpose of testing this. Eventually. Sigh.

Recently, someone told me chlorophyll utilizes the “A” band during midday sunlight, while the “B” band is utilized more in the morning and evening, when the “A” band is mostly reflected and/or absorbed by earth’s atmosphere. Anecdotal evidence seems to support this.

Here are some examples of LED fixtures people have made, and a few growth pics as well.

^^ That was how it looked at first, and below is how it looks more recently (9 days growth)

He stated that “due to the reduction of parameters, now my net grows quite thin, on the other hand not increased my biological load, so I assume that growth is normal”. Thin? Yes. Green? Yes. With CFL or T5HO, you would tend to get yellow growth.

^^ notice mostly shades of green. Only green.

My tanks: 120 Reef w/L2 Algae Scrubber, 60 Reef Pond w/floating Algae Scrubber, 40 Breeder Reef w/L2 UAS Tester Algae Scrubber
I maintain: 144 SW Reef w/L2 Algae Scrubber | 200 SW Reef w/L4 Algae Scrubber
Special knowledge: Algae Scrubbers, Acrylic Fabrication
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Old 02-19-2012, 10:13 AM   #43
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Again, patch growth, but only green.

Buy or DIY?

There is still a relative lack of selection in stock LED fixture that are satisfactory for our purposes, and an even greater lack when you’re trying to keep the cost low. So far, the only one I have come across that is even close is the 50W 4G grow light from e-Shine systems. This is a cheap fixture from China (usually between $100-$120 each, shipped) and has little track record. And like anything you buy from China, you get what you pay for, and if something goes wrong, chances are it’s easier to throw it away and buy another than to get it repaired. It does have a pair of fans on it, which means it can suck in moisture (and it’s not wet-location rated) and people have reported fan-cooled fixtures failing or the fans getting louder and louder over time (not just e-Shine fixtures, either). But, time will tell. For now, it’s what we’ve got available.

There are LED grow bars available (from China) that don’t have fans and are supposedly waterproof, but these are relatively new, and from what I’ve heard about them, they are not reliable. Also, they are generally only available in 1W arrays, and the density of LEDs is not enough. This might change in the very near future…we’ll see.

The 50W e-Shine fixtures are a tight array of 1W LEDs – 2 rows of 25 each, about 1/2” on center, 45 660nm Deep Reds and 5 455nm Royal Blues. What’s nice about this is that you can put it right up against the Algae Scrubber enclosure, within 2” of the screen, just like a T5HO. These definitely need to have acrylic or glass between them and the screen due to vent holes for airflow, and they weigh about 9 lbs each, so properly supporting them and protecting them from moisture is key to longevity.

There is a decent mathematical reasoning for going LED.

For initial cost, CFL and dome reflectors are the cheapest; clip-on dome reflectors are $10 or so each. Replacing lamps might run you as low as $10/year for a small Algae Scrubber, and as much as $30-$40 or more a year for a larger Algae Scrubber. CFL is the best low-cost alternative for the ‘cheap and easy’ build.

T5HO is more, either a stock fixture or end caps and reflectors, so your initial investment can be anywhere from $150-$220, then lamps are running currently about $5 each, and you need to replace those every 3 months or so (depending on the “on” time per day). If you have extra T5HO parts or fixtures laying around, then you could go with that. But setting aside the moisture concerns, going out and buying new for an Algae Scrubber has, IMHO, progressed past the point of diminishing returns.

Buying a pair of stock LED fixtures is going to run you $200 minimum, and could last years. Compare an Algae Scrubber using the 50W e-Shine 4G Grow bars to one using 2-lamp T5HO fixtures. Initial cost of 2 T5HO fixtures and 4 grow lamps will run you around $170-$220, and a pair of the e-shine fixtures about $220 (ballpark). T5HO lamps every 3 months will run you $20, or $80 per year. The e-Shine fixture break-even point is, at worst, just over 6 months. In the first 3 years, you can buy a pair of e-Shine fixtures for each T5HO fixture and break even. Just based on lamp replacement cost alone, the e-shine fixture only has to last 2.5 years to break even. It’s likely that a better product will be available within that time frame.

DIYing an LED array for a small Algae Scrubber might run you less than $100 and could last years as well. For the DIYer, there is a product that you can spray onto your fixture that makes it essentially waterproof. I personally don’t know much about this product but I have heard it works very well. If you feel up to building your own LED Algae Scrubber, at this point, I say knock yourself out. Just make sure you do your homework before putting pen to paper; study other designs and learn from the mistakes and successes of others.

As far as active cooling, for either a stock or DIY fixture, it would be ideal if the source of airflow to the LED fixture’s heatsink came from outside the sump or tank area. Not easy to do, and this is one inherent downfall of the LED Algae Scrubber.

3W versus 1W

With an Algae Scrubber, the goal is even coverage. CFLs have a bit of a problem in this regard, unless you use a good reflector. T5HO has few issues due to the linear nature. LEDs have an inherent issue with spotting.

One thing that is important to point is that 3 x 1W chips will put out more lumens than one 3W chip. Why? Because as technology has progressed, marketing has stuck itself in the mud. A 1W chip does not pull 1W and a 3W chip does not pull 3W. Some may argue this based on measured current and voltage drop, and I don’t want to get really technical here because by the time I post this, it will have all changed again (LOL).

3W chips need to be appropriately spaced and distanced from the screen to avoid spotlighting. The distance from the screen is the biggest downfall. You can put diffusion grating in front of the LEDs to help distribute the light better, but that also tends to cut down the intensity. Not much, but we’re going for best bang for the buck here. Lenses should be completely avoided (they only make spotting and burning worse). Most DIYers prefer 3W LEDs. Just space them out so that you get as even coverage as possible. The consensus seems to be that you need 1/3 to 1/4 the total wattage of 3W chips as you would fluorescent lamps for the appropriately sized Algae Scrubber. As previously mentioned, some even claim 1/5 the wattage.

I’ve been researching a bit on how many 3W LEDs you need to use. The general consensus at this point seems to be that you need one 3W LED on each side for every 15-20 square inches of screen. Going with the new feeding-based sizing guidelines, it seems that a simple technique would be to use one 3W LED on each side for every 12 square inches. So a 2-cube/day Algae Scrubber would need 4 3W LEDs, two on each side. Distance from the screen is something that depends on some factors, such as how hard the LEDs are being driven and how long of a photoperiod is used. New ground is being broken on this almost daily, and I am in the process of gathering as much information as I can from the DIYers so that some kind of ‘standard’ can be established.

1W chips are much better, IMO, for Algae Scrubbers, because you can pack them closer together, put them closer to the screen, and get near-perfectly even coverage. This mainly applies to off-the-shelf fixtures, which usually have one circuit board and the individual LED dies are close together. It’s hard to get 3/4” spacing using 1W chips on stars. But if you have ever had the opportunity to see a 1W LED grow lamp array in person, you would agree that they are bright as #@$&*^!%. I’m talking blindingly bright, and extremely even coverage. As far as the wattage comparison for those – not sure. The “1/5” numbers came from the DIY 3W LED folks…

Other thoughts on LEDs

Previously, I wrote that you probably should not rely on an LED Algae Scrubber for total filtration, only for supplemental filtration. This is no longer the case, not by a long shot.

Unless you are short on immediate cash and not comfortable DIYing some LEDs, there’s just no reason not to do an LED Algae Scrubber, in my opinion.

It is important to note that there has been no study that I could find that indicates what exact LED spectrum is ‘perfect’ for algae growth for this specific purpose. So there is a lot of new ground being broken right now.

Just make sure you realize that:

1) LED Algae Scrubbers do not have as long of a track record. Then again, the modern Algae Scrubber has really only been around itself for about 4 years.

2) Only recently have there been builds with any sort of success. However, some of those builds have been extremely successful.

3) Fixtures themselves are still not tested for long-term stability and reliability (mostly related to moisture issues)

4) If you build one, you’re going to be on the cutting edge, which can cut both ways. Take your time and think it through well, and don’t be afraid to ask a lot of questions.

There are LED floodlights available at the local hardware stores and other Big Box stores. Do not use these. This one below is a 3000K 75W incandescent equivalent, which equates roughly to an 18W CFL:

The problem is this: when it comes to LED, you have to throw the Kelvin rating out the window. It means nothing for Algae Scrubbers, it is only good for trying to match the color rendering given by a comparable fluorescent lamp that is used in a home or office. Remember, LEDs are a different type of light source and isn’t UV based and shifted with phosphors. Any LED lamp/bulb/floodlight/etc you can buy in a store that is not specifically a grow lamp is completely useless
My tanks: 120 Reef w/L2 Algae Scrubber, 60 Reef Pond w/floating Algae Scrubber, 40 Breeder Reef w/L2 UAS Tester Algae Scrubber
I maintain: 144 SW Reef w/L2 Algae Scrubber | 200 SW Reef w/L4 Algae Scrubber
Special knowledge: Algae Scrubbers, Acrylic Fabrication
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Old 02-19-2012, 10:14 AM   #44
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Electrical Protection

This should really go without saying, but you should always plug your lights into Ground-Fault protected receptacles (GFCI).

Always use waterproof sockets for your CFLs and end caps for your T5HO lamps. This is a little more expensive, but is necessary to avoid corrosion and electrocution. Generally, waterproof CFL sockets do a pretty good job of sealing the base and socket from moisture, but they still should be silicone sealed for an extra layer of protection. T5HO waterproof end caps do an excellent job of sealing the end of the lamp, but the wires that feed into the bottom of the sockets are not sealed, so after all wiring is complete, you need to fill in the bottom with silicone caulk.

You can't see it, but there will be tiny amounts of salt spray that will build up where you screw a CFL bulb in, and also where you make electrical connections. When the buildup gets thick enough, it can short out and trip a breaker or GFCI receptacle, or shock you. So each time you replace a CFL screw-in lamp, re-seal it. You should be able to pour water over it without it causing a problem (but don’t try it). Use GE Silicone I Door & Window caulk, which is generally accepted as aquarium safe, especially since you don’t intend for it to be in direct contact with water anyways.

Moisture protection for LED fixtures, DIY or off-the-shelf, is the biggest issue facing the progression of LED Algae Scrubbers. At this point, it’s just a risk that you either take or try to mitigate against. So far, no build that I have seen has incorporated adequate moisture protection, aside from passive cooling and spray-coating a DIY fixture.

Screen Break-in Period

Since the time frame by which you will see certain types of growth largely depends on the bio-load, initial nutrient conditions of the system, and strength of the scrubber, not everyone will see the same growth progression. Some have taken months to get a full screen of green growth; others get great results in just a few weeks. However, every screen must go through an initial break-in period, and that is relatively independent of anything else. Usually, the first week or two of growth is almost identical for any scrubber; after that, different system will tend to diverge depending on the conditions.

When you first start up your algae scrubber, even with the screen significantly roughed up, it is still relatively slick on a microscopic level. It is plastic, after all. The reason behind roughing up the screen is to vastly increase the surface area, and to give long strands of algae something to hold on to.

As the tank water cascades over the screen, there will initially be a buildup of brown slime, similar to what you see on the insides of your tank plumbing (and like what you clean out of your pump). Over time, this growth on the screen will strongly adhere to the screen. The bond is so strong that you would have to soak the material in vinegar to completely remove the algae. This may sound familiar to anyone running pumps or powerheads (which should pretty much include everyone).

During the break-in period, this brown layer is easily rinsed away (with a sink sprayer, for instance). For the first few weeks, a very light cleaning is all that is needed – just lightly running tap water. A gentle swipe of your fingertips will take most of this layer off, but will leave enough behind that if you put a new screen next to it for comparison, you will see a slight color difference. You want to leave behind anything that doesn’t easily wash away, including whatever is growing in the holes. You definitely don’t want to scrub the screen with a brush of any kind. Any growth you get for the first few weeks should be easily removed with your fingertips (not nails). If you happen to get some long green hair algae strands, you should be able to remove those with your fingernails (gently).

Usually after the second cleaning, the screen will have developed a foundation upon which algae will be able to form a good bond. What type of algae will grow next is dependent upon factors stated in the first paragraph of this section. Regardless of the type of growth, the screen will continue to mature to the point where if and when a thick mat of algae grows, it will stay firmly attached to the screen. This is usually attained around the 4-6 week point, and can be verified when algae grows inside the ‘squares’ of the screen and does not come loose during cleaning.

My screen break-in cleaning technique progressed as follows:

Week 1: Rinse with slow running tap water

Week 2: Same, except used fingertips to rub screen

Week 3: Rinse off with running water, then rub with fingertips

Week 4: Same

Week 5: Same, had to use backs of fingernails in some places

Week 6: Algae firmly attached. Used back of fingernails across entire screen (now I use a plastic scraper)

Every scrubber will have slightly different growth progression, but the guideline above gives you an idea of what to expect. See “Algae Growth Types” for some additional information.

Cleaning the screen

Cleaning the screen should be done remote from the tank. A common complaint of the past was that an Algal Turf Scrubber turned the water yellow, but that was because algae was generally removed from the tank with the screen in place, or it wasn’t well rinsed.

If you have lots of pod-eaters in your tank, and your screen is nice and green (no slimy growth) you can consider swishing the screen in the tank every once in a while before cleaning. I did this a few times, but I really don’t anymore.

Screen cleaning should be done in room temperature tap water. The reason is that freshwater kills pods that are continually munching on the screen. There will be millions more in no time, you just don’t want them causing algae to detach between cleanings.

I use a cutting board and a plastic pot scraper similar to this one https://www.pamperedchef.com/orderin...Id=241&catId=9 to scrape the algae off the screen.

You will need to use an old toothbrush or a stiff-bristled scrub brush to remove any algae that grows on the smooth area at the top of the screen. I also use a scrub brush to remove any red turf. Red turf seems to grow well in the lower light areas. I have since trimmed these areas off the screen since I needed to make it smaller.

The slot tube also should be cleaned by scrubbing with a brush and rinsing. If you have an enclosed box device, you will likely need to clean algae out of there occasionally too. I have to do this every cleaning, it’s amazing how well algae attaches to a smooth surface.

After all the scraping and scrubbing is done, give the screen a good rinse (15-20 seconds) in fast running water.

Cleaning frequency

For the first 4-6 weeks, cleaning every 7 days is probably a good idea (see the ‘Screen Break-in Period’).

The exception is the ultra-high nutrient system that results in a black slime coating forming every 2 or 3 days. Such growth must be completely removed, as soon as possible - at the most every 3 days (see “Algae Growth Types”)

The general rule has been to clean your screen every 7 days. This is still the rule for single sided and non-vertical Algae Scrubbers.

If you run a double-lit vertical Algae Scrubber, now it is allowable to let the screen grow as long as 10, and in some cases, 14 days. Again, you need to pay attention to your screen growth, and that it as simple as checking it once a day, because the frequency of necessary cleaning relates to what kind of growth you’re getting.

I nice, thick mat of emerald green hair algae does the best filtering.

Regardless of growth type, as the algae mat grows thicker, the outer layers block light (and flow) to the lower layers, specifically where the algae attaches to the screen. This causes weakening of the strands, which can lead to algae detaching from the screen. This is more likely to happen with a single-sided screen, because the light intensity less at the screen level. It is less likely to happen in an enclosed-box 3D growth type system, as the algae is supported a little better.

What really tells the story is what the algae mat looks like when you clean it. If you are regularly cleaning off a thick mat of green algae that is firmly attached to the screen, you can probably let this go for a few more days between cleanings. Increase by one day at a time and monitor closely. If the algae becomes a lot easier to clean off, or becomes straw-like near the screen, this means the algae in the lower layers is not getting enough light and/or flow, and is dying, and you’ve reached (or possibly exceeded) the limit on how long you can go between cleanings.

If you are getting a thin layer of algae, but it’s not too dark (maybe a darker green or thin and brown, and you can still see the screen) you can let the screen grow for a few more days. The key here is that as long as light is penetrating all the way down to the algae attached to the screen, you can let it grow. You want to allow the green algae, however much you are getting, a chance to grow.

If you are getting a little thicker mat of brown growth, don’t go over 7 days. Same goes for the yellow, rubbery growth. You can clean these more frequently than 7 days; try to leave as much green hair algae that you have on the screen. If you are getting black, slimy growth, clean about every 3 days.
My tanks: 120 Reef w/L2 Algae Scrubber, 60 Reef Pond w/floating Algae Scrubber, 40 Breeder Reef w/L2 UAS Tester Algae Scrubber
I maintain: 144 SW Reef w/L2 Algae Scrubber | 200 SW Reef w/L4 Algae Scrubber
Special knowledge: Algae Scrubbers, Acrylic Fabrication
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Old 02-19-2012, 10:21 AM   #45
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Slot pipe clog prevention

This issue is brought up on a pretty regular basis. Obviously, no one wants an overflow pipe to clog and overflow their tank. Most people take precautions to prevent livestock from entering the overflow pipe, such as an intake screen. In the case of the scrubber, they’re worried about the algae growing thick enough to stop flow at the point where the screen and pipe slot meet.

Almost without exception, this question is posed by someone who studies the design, but has never actually built or operated a scrubber for any length of time. I’m not trying to belittle anyone posing the question by saying that, rather just making the point that if you run a properly built scrubber, you’ll understand that this is really not a concern. Here’s why:

If you properly build and maintain a scrubber, there is virtually no chance that algae will grow thick enough to block the slot. I’m not saying that algae will not grow at the junction point of the slot and screen, it most certainly will to a certain extent. The water on the screen below the slot will get partially diverted over the top of the algae mat, as water takes the path of least resistance. As you approach the slot, the flow area is restricted to the narrow space between the pipe slot and the screen. This creates an area of flow pressure under which algae cannot grow to any significant thickness without succumbing to the pressure of the flow and releasing from the (smooth) screening material. Proper cleaning of the slot and the smooth portion of the screen during weekly screen cleanings virtually eliminates any chance of the slot clogging.

As for the interior of the overflow pipe and slot pipe, these can be clogged by variety of means. The most obvious of example is a snail, anemone, or other tank mate that makes its way down the pipe. This is a potential problem for any overflow pipe, but adding a slotted pipe with a cap on the end just makes some people nervous, because there’s no place for that obstruction to exit the overflow pipe. Fortunately, this is only a problem when you insert the screen too far into the slot pipe. If you only insert the screen far enough that is extends about 1/8” to ľ” above the inside of the pipe, then anything that makes it all the way through the plumbing to the slot pipe will get pushed to the end of the pipe by water pressure, and should only partially block the flow, and only at the end of the screen, if at all.

If you insert the screen all the way into the slot until it contacts the inside of the pipe, the obstruction could form at the beginning of the slot tube, and could substantially or completely block the water flow. However, this is perfectly fine as long as the inlet to your overflow pipe has a strainer on it that would prevent anything from entering the pipe.

I don't know if there is any advantage to full insertion vs. minimal insertion. Inserting the screen further into the slot pipe may even the flow out a bit, but I haven't noticed any glaring issues with the way I do it. This is why I recommend inserting the screen such that it protrudes no further than ľ” into the interior of the slot pipe.

With all that said, if you’re still concerned about the issue, and don’t want to take any chances at all (and you would be hard pressed to find someone to blame you), then there are a few techniques that can be implemented that will reduce or completely eliminate the chance of a blockage of the slot pipe causing your tank to overflow. Notice that I only mention a blockage of the slot pipe. This is because a blockage of the overflow plumbing before] the slot pipe is a totally different issue, but some of the solutions below will apply to both.

Screen modification

You can remove some of the horizontal pieces from the smooth section of screen, the idea being that with the horizontal portion removed, there will be a faster flow of water and less area for the algae to attach to. Something like this:

The larger open space means that cleaning off the algae that grows between the squares is much easier. I haven’t seen many people use this technique, and haven’t had much feedback either way, but I would expect that this could result in slightly less flow impediment at the junction point, which might mean slightly higher flow requirements in order to get even flow coverage. But that’s just a guess.


Originally, it was recommended to place crosscuts in the slot tube. You will see this on older builds. This is not recommended anymore, so don't do it. The idea was to allow for water to continue to flow if the algae grew up into the slot and clogged it, and also to prevent squirting. The result was that algae grew easily into the slot, because the pressure wasn't high enough to prevent it - flow was just diverted to the crosscuts. Then, the pressure was higher through the crosscuts, which resulted in squirting. In essence, crosscuts created the problem which they were supposed to solve. This is basically how the concept of pressure preventing growth (as described above) was brought into focus.

Herbie or BeanAnimal

The best way to run a scrubber, for more than one reason, is to feed directly from the full siphon standpipe of a Herbie (2-pipe) or BeanAnimal (3-pipe) system. I don’t want to go into a large amount of detail about these systems, or debate the advantages or disadvantages, so I’ll just briefly describe them.

These systems utilize the concept of the “tuned” standpipe; the first standpipe (“Siphon”) has a valve on it that can be adjusted until the rate of flow through that pipe is just below the rate of flow of the return pump, and the second pipe (“Open”) handles the excess without gurgling and flushing. The BeanAnimal system uses a third “Emergency” standpipe and has a modification to the “Open” standpipe that allows that pipe to “take over” as a full siphon in the case of a total blockage of the “Siphon”.


These systems are designed with a backup standpipe that is able to handle the full flow of the system in the case of a partial or total blockage of the main siphon pipe. This allows for the full head pressure of a column of water above the scrubber slot, which results in a higher pressure at the slot and even less chance of algae growth near the slot.

There are other considerations when running a scrubber off a tuned pipe system that I don’t want to get into here. I just wanted bring that option to light.

Slot pipe bypass

On some early designs, you can see a PVC tee in the overflow pipe for an “emergency” or “clog bypass”. The thought process was similar to the “crosscuts” idea, in that water would flow through the “bypass” if the slot pipe got clogged with algae growth at the pipe/screen junction, and the result was the same. What would usually occur is that the “bypass” would run very easily and not allow pressure to build up at the pipe/screen junction, and occasionally it would divert flow completely. This also helped bring “pressure preventing growth” into focus, and thus it is not recommended.

However, there is a modification of this concept that will allow the pressure on the slot pipe to stay high, while still allowing for an “emergency” or “clog bypass”. The key is that the alternate branch of piping must be as high above the slot pipe as possible, and must not be a closed pipe (or it will siphon).

Here is a sketchup of the basic concept:

The left side represents the overflow pipe that directly feeds the scrubber. The first PVC tee can really be placed anywhere with any orientation, but lining up the primary flow through the ends is best, with the bypass flow coming out of the side of the tee. The bypass line should then elbow upwards as high as possible, then elbow over to horizontal into another tee. The pipe below the second tee extends to the sump. The pipe above the tee provides an anti-siphon relief and should extend to the top of the trim on the tank. The bypass pipe should be one size larger than the rest of the plumbing from the point of the second tee to the sump, at least in my opinion.

If the overflow is from a drilled bottom / reef-ready tank, this means that you will have to run the bypass pipe up about 1/2 way up the back or side of the tank, keeping in mind that the level your standpipe/durso inside the overflow in your tank will need to be several inches higher. If you’re running this of an HOB type overflow, you still want the first tee as low as possible, but since you already have the back of the tank to work with, you can place it before you elbow towards the sump, then go vertically up the tank and elbow over to the second tee.

The important concepts to follow here are 1) the second tee is higher than the first, preventing free-flow through the bypass, 2) the second tee is high enough to prevent unwanted bypass, 3) the bypass line is not allowed to easily form a siphon, and 4) the bypass line should be able to handle 100% flow from the tank in case of a blockage before the slot pipe.

All pipes should be welded (not friction fit) and appropriately supported and secured in place, such as with straps or clamps on the stand or a wall.

End of Summary

Well that’s it for now. I tried to incorporate as much as I could into this one. There might be a few things to add down the line before the new version is released. Also people will continue to use the older version and there will undoubtedly be helpful hints that come up along the way, so there’s no ruling out a second part.

Happy Scrubbing!
My tanks: 120 Reef w/L2 Algae Scrubber, 60 Reef Pond w/floating Algae Scrubber, 40 Breeder Reef w/L2 UAS Tester Algae Scrubber
I maintain: 144 SW Reef w/L2 Algae Scrubber | 200 SW Reef w/L4 Algae Scrubber
Special knowledge: Algae Scrubbers, Acrylic Fabrication
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Old 02-19-2012, 03:19 PM   #46
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Good stuff...So it is your opinion that even though i have been successfully scrubbing for a good while now with CFL's and dome reflectors ,i should switch to an LED scrubber...What ever happen to "if it ain't broke ,don't fix it"...IDK,,i very pleased with my current set-up and it works great...I'm all for new ideas though..
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Old 02-19-2012, 03:39 PM   #47
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+1 to that!! Keep going if it works. For new builders, just some things to thing about. CFL is still viable and easy to do.

LED is just as easy as T5HO since it usually involves an enclosed box scrubber, so you're already in a more advanced line of thinking, therefore being able to DIY or buy your LEDs means T5HO is pretty much dead IMO.
My tanks: 120 Reef w/L2 Algae Scrubber, 60 Reef Pond w/floating Algae Scrubber, 40 Breeder Reef w/L2 UAS Tester Algae Scrubber
I maintain: 144 SW Reef w/L2 Algae Scrubber | 200 SW Reef w/L4 Algae Scrubber
Special knowledge: Algae Scrubbers, Acrylic Fabrication
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Old 02-19-2012, 09:59 PM   #48
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First off, thanks for all your hard work and for sharing all of this info, I'm currently building my first ATS and have this thread has helped me sooo much!

I am no expert (AT ALL) on lighting but am currently using a 10w 5500k LED flood light (like the one pictured below) in my refugium and it has been growing desired algae like crazy. I figured I would give it a try on my ATS that I'm building.

I have found this one on eBay and am considering giving it a go, would the red one be sufficient for all the ATS needs? Or should I get a soft white with the lowest k rating I can find instead (believe they only make them as low as 4500k). Is 10w overkill on an 8" screen (double sided)?

Any thoughts?

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Old 02-19-2012, 11:53 PM   #49
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Good update. I'll be waiting for the next update for the better version of this basic concept.
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Old 02-20-2012, 04:35 PM   #50
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Tom,, that looks like it uses about 9 1W LEDs, 3 of each color. Basically the green is useless though. So you're left with 6 1W LEDs, and you don't really need an equal ratio of the blue, so the reds are doing the majority of the work. If you feel like trying it, I would be interested to hear how it works. If it seems to work well for your fuge, I would give it a shot if it doesn't cost too much.

About the K rating, that mainly only applies to fluorescent lamps. The reason you see it with relation to LEDs is that people are 'used to' seeing that kind of rating, and it only really applies to the residential/commercial lighting field where people want to replace their lighting with LED, yet make it look the same. You will see Cree's literature reference K ratings but this is the same thing. The K rating is how a light looks in color to us, and is achieved by blending phosphors, and you can achieve the same K rating using different combinations of phosphors.

This method does not directly apply well to LEDs and algae, because you could have an LED bin that is right on 3500K, yet it will not have very much useable red.

What it comes down to is that there is enough strong evidence that 660 red works, and there is a varying degree of results from other LEDs. This led me to making 660 LEDs the current standard, and until evidence shows strongly otherwise, I'll continue that recommendation.

I just ordered a batch of supplies from RapidLED and HeatsinkUSA to make 2 'tester' scrubbers, one will handle 1 cube/day and the other 2 cubes/day. I am also building one using the e-shine fixtures, and have 2 custom 4-band 112 1W LED fixtures that I will be using to test spectrum effectiveness.

My tanks: 120 Reef w/L2 Algae Scrubber, 60 Reef Pond w/floating Algae Scrubber, 40 Breeder Reef w/L2 UAS Tester Algae Scrubber
I maintain: 144 SW Reef w/L2 Algae Scrubber | 200 SW Reef w/L4 Algae Scrubber
Special knowledge: Algae Scrubbers, Acrylic Fabrication
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