How much light is enough? The 2WPG debate.

[Purrbox]

An earlier thread went a bit off topic in a rather interesting direction. In order to quit hijacking the original thread and still give the topic a chance to be discussed, I'm starting this thread. Original thread found here.

I know no one "needs" more than about 2w/gal to grow any plant.........
So why more?
Means you have to prune more, less wiggle room dosing/CO2 etc/higher risk of algae etc.

I think that a large part of this is that most people don't realize that you can grow the "high light" light plants with less light. We're constantly told that in order to grow a nice low lawn of glosso, etc we have to have 4+w/gal or it will grow up. Of course then some people try to grow it with less light, and it does grow up. Or there that really neat plant that requires high light, and dies if someone tries to grow it with less light.

Now I think the question is, why are you able to grow these plants sucessfully with less light while others are failing. The obvious answer is that light is the easy scapegoat. Perhaps there are other factors that aren't being addressed adequately, or aren't addressed adequetly until that same person ventures into high light. From what I've seen from your posts lately, it appears that CO2 is your chosen scapegoat. Since most people are extremely reluctant to try CO2 until they are forced to do so by venturing into high light, this would make a lot of sense as the missing piece to the puzzle.

So is the answer medium light with CO2 and good nutrient levels? Will this allow us to grow all the plants we might want to try and get the results that we want? If so, then the key is for more people to try it, be sucessful at it, and be vocal about their success. Until we start hearing the same thing from more people the message will keep getting drowned out by the majority and we'll keep following in the footsteps of our peers to the grail of high light.

I'll be the first to admit that I'm still very new at growing aquatic plants. I've got a lot to learn yet. I'm finding some sucess with some plants that could be considered difficult or rare, but I'm also still learning how to grow plants instead of algae. I'm also foolishly trying to do all this learning on extremely small tanks that I wouldn't recommend to anyone else, because I don't have the space for a larger tank. It's a steep learning curve, but I'm making progress and I'm stubborn enough to stick with it to try to get things figured out.

If your theories help me to fill in the holes and learn to grow plants better, great! Unfortunately I still have so many holes still left to fill before my picture is complete.

I've been growing plants in less than 2wpg for two years.

I would love to have the "grow all plants in 2wpg" addressed in it's own thread. Looks pretty informative.

Let the debate continue!

 

[kennef]

Purrbox, this is a great topic, and i think you really struck a chord about light being the easy scapegoat. If all of the different factors absolutely had to be met to meet with some kind of success, we might see about 3 people posting pics of their wonderful plants, instead of the many that we do see. it's true that some basics must be met, but beyond that its a matter of fine tuning a process that works within your lifestyle. we all know if it doesn't fit that, you wont last long with it, right?

i am incredibly pleased to see people doing things their own way, then coming and sharing what worked for them and what didn't. i for one have enjoyed my plant growth in spite of using techniques and equipment that might not be exactly the same as others. thats the beauty of this hobby, really. With that in mind, i still have to say that the information on this forum exceeds all expectations as far as accuracy and usefulness.

So, per your suggestion, i wish to be vocal about my success with growing plants not in low light, but with screw in 6500k CF bulbs. I agree that there may be some truth to the idea that light is lost in these bulbs due to restrike, however i cannot deny that my 30 gallon is growing up, out and over flowing with stargrass thanks to 5 24W CF bulbs. i figure even dropping 30W due to restrike would still put me at 3WPG, and so far its been dandy. I think that its a fair trade for the initial price savings over something like a PC fixture initially... though i might never suggest it to a beginner. but i think for me, half the fun of this hobby is the DIY aspect, so it becomes a double pleasure. I know some of the DIY goup have had great success with ODNO as well, and i might try that myself someday. i do know i am wanting to try at least 1 tank with a PC fixture just to compare, because i really want to have a frame of reference.

Anyway... thanks Purr.. this is a great opportunity to find some common ground and ideas for tweaking with all of you...

 

[Glenc]

I have 7 tanks on the go now, I agree, you can grow most anything with 2 wpg. I'm doing it. It sets a very managable pace. However, I am still drawn to using way to much light just for the challenge of it. Half of my tanks are very high light, 4wpg+. Takes a heck of alot more work, but they are running smooth. Call me a glutton for punishment, but I just love the glow, beauty and colour of a tank lit up with 4wpg. I am a high light junky

 

[JDogg]

i agree, all my planted tanks are between 2 and 2.5 wpg, some with CO2 some without, i have yet to try a plant that would not grow.

 

[Wizzard~Of~Ozz]

Went digging for some of my old posts..

Co2 can increase plant growth More then increasing the light levels (at least according to tropica)

http://www.tropica.com/article.asp?type=aquaristic&id=142

is an excellent read on the benefits of Co2.

Co2 has more of an impact at low light then adding more light, but once you add Co2, the next step is adding light before you increase the Co2 levels. (Moderate Co2, Low Light = better growth then Moderate Light, Low Co2)

second quote was on Feb 13, 06 Here


There is a nice layout in the link (and some charts) that show the differences noted.. They would concur (that medium light will grow a lot w/ adequate Co2.) except for a minor issue that draws back to the original problem..

Growing a healthy plant, and growing a plant a certain way (Glosso is a good example) often have different requirements, this depends more on light pressure then anything else.

One thing I've always done is tried to push Co2 into any planted tank. It is a requirement after all (I'm sure some can get away with not using it, but only in a tank that has 1 maybe 2 plants with low light and extremely slow growth.) Realistically, plants consume carbon, if there is none or levels are extremely low then Only the strong survive and algae has been around for a very long time. I can see why Tom believes that Co2 is the "root of all problems".. it just makes sense as a very common deficiency if it isn't added. I wouldn't say it is the source of all Algae, but it is probably the most common cause in a planted tank.

To quote the last bit of that article I linked to (section 4)

It is often a much more difficult and expensive task to provide adequate light over the plant aquarium. Both fluorescent light and highpressure-quicksilver lamps may produce sufficient light if supplied with effective reflectors but in deep aquaria (more than 50 cm) is very difficult to offer enough light to small light demanding foreground plants. Based on our experiments, we suggest commencing CO2 addition before any other action is taken! We believe that even at very modest light intensities you will experience a conspicuous change in plant performance in your aquarium. The exact amount CO2 may always be discussed but if you do not have very sensitive fishes in your fish stock, concentrations from 25 and up to 50 mg/l will only improve plant growth. You will probably see that plants, which were barely able to survive before now, thrive in the presence of CO2.

 

[Jchillin]

I've been growing plants in less than 2wpg for two years.

I would love to have the "grow all plants in 2wpg" addressed in it's own thread. Looks pretty informative.

And with good reason. I will give an example with two pics of a group of Lymphaea plants that I introduced a few weeks ago when I changed out my nice blue substrate.

Lymphaea before:

Lymphaea after:

Tank is 75g with 1.5wpg. The plant grew, so there is no doubt in my mind that the premise on it's own merit is correct. As most members know, I have been experimenting with traditional "high light" plants to see if I could grow them in low-light environments. The Lymphaea is the first one that has achieved this type of growth. Others did not grow so fast or were able to maintain their original coloration.

 

[SparKy697]

This is a great post.

I have been "growing" Stargrass is a 10g tank with < 2wpg, no co2, no ferts, and only an occasional shot of excel for three or four months now. It has shown growth, but much different than clippings from the same plant has in a high light, co2 injected, EI dosed tank.

The stargrass in this tank is very dense and compact. What you see is more than three months of growth without a single trimming. This is the only plant I have really tried so far. There is also some Bacopa and a few other plants in this same tank who are all doing well too.

Being relatively new to the planted tank world, I have found no shortage of advice telling you how it must be done for success. We must be careful with words like "always" and "Never".

 

[Sidi]

I have a Madagascar lace that grows like crazy at about 2.3 w/g with minimal ferts and no CO2 (Excel though). Najas and hornwort grow like weeds.

I think it really is possible to grow most things at 2 watts/gallon. You may not get the color in a plant like a sunset hygro, but for the most part things will grow at "medium" light.

 

[czcz]

I think it really is possible to grow most things at 2 watts/gallon. You may not get the color in a plant like a sunset hygro, but for the most part things will grow at "medium" light.

If we agree high CO2, low NO3 , high PO4, or whatever can also produce reds, consider how much easier it is to control nutrients at 2wpg than, say, 4wpg. Plus, Sunset Hygro grows too fast at 4wpg to be scapable anyway.

 

[TTKarl]

Ok here's my 2 cents. For one the wpg theory i think is only a guideline. Tank size definitely makes a difference! I also wonder about outside light. I know even with my light off my tank gets some indirect sunlight vs some people who have tanks in there basements.

As far as glosso goes mine is currently forming a pretty nice carpet at 2.5 wpg and is only growing up where it has spread into shaded areas. I have yet to find a plant that has failed in my tank due to lighting(or at least from what i can tell) I have noticed some better coloring when some plants reach the top of the tank namely rotala.

Not too get off topic here imo for what it's worth, i have not run into any limitations at 2.5 wpg.

 

[Jchillin]

Not too get off topic here imo for what it's worth, i have not run into any limitations at 2.5 wpg.

Fortunately, that is the topic.

 

[LandGhoti]

I have 2.2 wpg, no CO2, and dose Flourish every three days, and may start dosing Excel (need to read more posts about it, LOL). I have seen crazy growth of everything in my tank.

I have yet to find a plant that has failed in my tank due to lighting(or at least from what i can tell) I have noticed some better coloring when some plants reach the top of the tank namely rotala.

Totally agree. My rotala gets lavender up there, and I've noticed a couple of strands of my L. repens finally returning to their original state of turned-up leaves that are a beautiful red beneath; of course the other strands are a beautiful green, but that is all . This makes me v. tempted to up my lighting, but I'm not sure I want the CO2 commitment yet, so am trying to enjoy my tank the way it is.

 

[Purrbox]

I find it interesting that so far only Glenc, Jchillin, and SparKy697 have actually supported this idea with tanks that are using 2WPG or less.

While most of the others have provided of examples of tanks which aren't decked out with 3WPG or more, they still have more light over them than the originally stated limit of 2WPG necessary to grow plants. As such while they do support the idea that high light isn't necessary, they also don't support the idea that it's only necessary to have 2WPG of light over a tank to grow any plant you choose.

It would be good to hear more from those that are keeping tanks that are within the stated lighting limits. What kinds of more difficult plants are you keeping? What is your care routine? What kinds of results are you getting?

 

[dapellegrini]

Hmmm....

First a bit of a clarification. It seems to me that we are attempting to define the "point-of-diminishing-return", where adding more light would be counter-productive to our goals and aspirations as aquatic gardeners.

Second, if we are to use WPG as our benchmark, are we using the accepted multipliers for different types of light, where it takes fewer watts of CF to achieve the 2 WPG measure? I am assuming at this point we are infarct making this adjustment in our discussion.

As for our "goals and aspirations as aquatic gardners" - I think we need to set a point of reference. First thing that comes to mind is Amano/Nature Aquarium, as I think most people would be extremely happy to find themselves capable of reproducing something of this type. If we agree that this is a good "generic" measure, then this link: http://www.fitchfamily.com/lighting.html which I believe I got from someone on this site, lends some good insight.

Average lighting used by Amano for some common tank sizes:

3-gallons: nearly 13 WPG
10-gallon: 6.5 WPG
20-gallon: 4.5 WPG
55-gallon: 2.6 WPG
75-gallon: 2.2 WPG
120-gallon: 1.7 WPG

Now, the author does not clarify if s/he is making our WPG adjustments, but if s/he is not, and we figure that Amano is typically using CF fixtures, then the numbers look like this (1w of CF = 1.75w):

3-gallons: ~23 WPG
10-gallon: ~11 WPG
20-gallon: ~8 WPG
55-gallon: ~4.5 WPG
75-gallon: ~4 WPG
120-gallon: ~3 WPG

All of that to say that there are a lot of factors involved here. Where exactly is the point-of-diminishing-return? Depends on the size of your tank. If we mean to discuss the average 55-75 gallon aquarists, it appears that 2-3 WPG of CF lighting should be adequate to do what Amano does.

Of course if your ambitions are different, I think the point of reference changes. If you want to grow Crypts, Hygro and Moss, less light would suit you fine. If you want to grow Cabomba Furcata, Tonina, or explore other high-light options 4 WPG of CF lighting is not overkill in our 55-75 gallon middle-ground, IMO.

To Purrbox's question, How many of you are growing these plants successfully at or under 2 WPG (considered High Light plants):

http://www.plantgeek.net/plantguide_list.php?category=1&filter_by=6

And anyone doing these at 2 WPG? :

http://www.plantgeek.net/plantguide_list.php?category=1&filter_by=7

** EDIT **

I should also mention that relevant examples should be with plants that have been growing for at least a month or two. Back before I had any idea what I was doing with plants, I could keep a group of non-aquatics looking good for a month or more.

To say, it doesn't count if you just bought a gorgeous plant, plopped it under your limited lighting and woke up the next morning to find it still alive and well.

 

[Plantbrain]

ADA seldom uses harder Tonias etc, they use plants that are suitable for scaping, Amano also does not add all the light , only for 3 hours at most, after the CO2 has buolt up for several hours at say 1-1.5 w/gal at most.

So overall, they are much lower light than the above figures...........and that is the rest of the story..............

Horticulture for aesthetics rather than speed of growth/growth rates are two very different thing as you can swap species also to address less work also.

I'm not sure why so many folks want so darn much light...........it causes them problems and few if any ever change to lower light, running headlong into insanity.

Regards,
Tom Barr

 

[Wizzard~Of~Ozz]

I'm not sure why so many folks want so darn much light...........it causes them problems and few if any ever change to lower light, running headlong into insanity.

Regards,
Tom Barr

It's the American way isn't it? More is better, even more is even better.

The reason I see for more light is for effect as I stated earlier (carpet effect).. colouration can also be a factor.

That's not to say it can't be achieved a different way, but this is the way that most people will look at the problem, and solve it. Most plant companies and informational sites promote the insanity by pushing out phrases like "Will grow to beautiful colours if enough light is given" and "High light and Co2 will help promote faster growth" for some slow growing species.

 

[Purrbox]

dapellegrini - you bring up some very good points. I think the multiplier that you're using for CF is rather high and probably based on either the least efficient T12 fluorescents or the most efficient CFs. Using a multiplier of 1.35 would probably be a lot more reasonable based on the average efficiency of both types of lighting. Reguardless, as Tom has mentioned, Amano only uses the total amount of light over his tanks for a very short noon effect at the middle of the day. A more produtive question is how much light does he use over his tanks the rest of the day? I suspect that this is probably one of the many reasons why so many of us have been lured into high light setups. Since we get so little data about Amano's tanks which is often incomplete, we end up trying to model our tanks after his without having the complete picture. The other factor is that his tanks are often setup with a very short life expectancy. Amano doesn't expect to have one of his tanks setup for more than a year or two at most.

Tom - I've seen some beautiful pictures of plants from your tanks that are extremely healthy and have absolutely brilliant red colors. Are all of these being grown with the maximum 2WPG that you are recommending?

 

[dapellegrini]

I'm not sure why so many folks want so darn much light...........it causes them problems and few if any ever change to lower light, running headlong into insanity.

LOL. Perhaps a different way of looking at this, that supports what Tom is saying here, I run high-light (324w of T5-HO over 72-gallons) and have found that my plant selection has become limited to those that are considered difficult or slow growers. In the beginning I really enjoyed the rapid growth and high-maintenance of most plants, but it does get old quick. As an example, I most recently got rid of my Parrots Feather as it was growing 3-4 inches a day. I also got rid of my Glosso for similar reasons.

Now, I spent a little bit more on a fixture with multiple switches, which allow me to control the quantity of light that I use. I have scaled my light down considerably since the beginning, but still blast a lot of light in there. I have found that using high-light gets me the best compact growth with many plants and leaves me the most options overall.

Problem I see with this discussion is the complexities of light - size of tank - depth of tank - type of lighting - etc. I just don't see 2WPG being a simple formula across the board. I do agree that you can have great success with many plants (perhaps up to 80% that are common in the hobby) with less light than many of use end up using, of course assuming all of the other factors are correct.

** EDIT **

The 1.75 factor was grabbed from another source (maybe WoO)... Whatever the acceptable factor, I think the point is still valid - trying to make sure that we are all talking about the same thing with WPG...

Also, even if ADA is only blasting full light for a portion of the day, wouldn't this still mean that you would need a fixture capable of higher wattage to accommodate this? Not that you need to run all the lights for 12 hours a day, but if you don't have the extra light, it sounds like you would still have problems trying to reproduce an ADA style tank. All of that to say I think when buying a fixture, the numbers I listed above are the valid levels you should be buying regardless of the cycles you setup (which is another good topic).

 

[Plantbrain]

That's why I use a PAR light meter instead of Lux or other inappropriate units such as watts.

For tank's in general using normal FL's, the w/gal rule of 2w/gal is fine.


Regards,
Tom Barr

 

[Wizzard~Of~Ozz]

1.75 was a very early estimate. 1.35 was the calculated value, and T8's are actually better then CF (on paper)