DSB vs Plemum

[cybercron]

I am ready to remove my CC, it is a breading ground for algae and a general mess. This is aided by my inefficient protein skimmer, which I intend to replace. Anyway, I have decided to convert to the live sand model. My first question is do I create a plenum or a DSB? Also, has anyone had a problem with fine grain sand damaging filters and PH's? My LFS is trying to talk me out of the live sand model and into a UGF.

 

[possum]

i have had no problem with sand except when i kept african cichlids and they stirred it up alot but in sw it usually stay put pretty well

 

[captivereefs]

DSB. Even though they are a topic of debate right now the work. Mine has been up for 6 years. No problems and no nitrates or phosphates. My freind has a plenum that is 3 years old. It is a mess that i do not even want to go into! Stick with the DSB and pick up a better skimmer. Stay far far away from an UGF. The sand grains should do no serious damage to your equipment.

 

[loganj]

The only thing worse than a UGF in your tank would be...maybe a couple of gallons of used motor oil. OK, that's a bit extreme, but you don't want to go with a UGF. It will cause you grief in the long run. There are arguments for plenums and DSB's. Either will work and control nitrates if set up properly. I have never used a plenum, but I have several tanks using DSB's and they work. You'll need to get some good live sand...not the bagged stuff. Use sugar sized sand to get a depth of at least 4" with 5-6" being better. Get a cup of sand from as many established reef tanks as you can to seed the DSB. You can also order detrivore kits from online retailers. Nassarius snails are good too. The sand will be easily stirred up for a short while until it gets a coating of bacteria on it. Then it will settle nicely and you shouldn't have any more problems with it. Just make sure your PH's are high enough that they don't suck up sand off the bottom. I would strongly suggest doing all the research you can about both plenums and DSB's before you make a decision. Just a Google search will probably turn up more than you wanted to know.

 

[cybercron]

First off, I want to thank everyone for all of the responses. This board is the best. Anyway, I originally wanted to go DSB. I did the Google search and started reading about the great DSB vs Plenum debate, which led me to this posting. I am going to stick to my original plan and create a DSB. First, what size sand to use, #0 Extra Fine grade or #1 Fine grade (I am not sure which is sugar sized)? Second, I was going to use bagged live sand from either "live aquaria" or my LFS. Logan mentioned something about not using the bagged sand. I also intend to use the steps provided by Kevin Colagio in the "Converting from UFG to a DSB" document to guide me in my conversion. I will continue to search Google to pick up tips and tricks until I am fully comfortable with the change. All of my denizens are happy ATM.

 

[biotoxin]

Alot of people are moving toward a more shallow sandbed around 1". It doesnt become a nutrient sink later down the road and its easily replaceable if something does happen to corrupt the sand bed.

 

[wseaton]

My first question is do I create a plenum or a DSB?

How can you create a plenum without a DSB may I ask our resident experts?

I don't think you'll find a lot of disagreement on this board that DSBs do the job. About our only debate on the topic is how deep they actually have to be to get the low oxygen, nitrate reduction effect. Personally I think the 5-6" recommendations are over-kill with the real optimum depth being significantly less. I also think the DSB in a plenum system is doing the real work while the plenum accomplishes little.

For the optimum DSB you want ooltic sand, and as far as I know there's only one grade of the stuff; fine.

The big problem with using dry sand is it's an unstable as hell until the tank breaks in and it settles in. After the tank matures it's no worse than having CC or even large gravel in terms of stability. However, for the first several weeks if not month or two dry sand is a mess in a tank and will cloud up if looked at funny and this *is* a lot of wear and tear on your filters. To get around this problem use wet/live sand to top off your sand bed while freely using dry sand as tha main base.

The only thing worse than a UGF in your tank would be...maybe a couple of gallons of used motor oil

Motor oil produces fewer nitrates

 

[loganj]

I don't think you'll find a lot of disagreement on this board that DSBs do the job. About our only debate on the topic is how deep they actually have to be to get the low oxygen, nitrate reduction effect. Personally I think the 5-6" recommendations are over-kill with the real optimum depth being significantly less. I also think the [acronym="Deep Sand Bed"]DSB[/acronym] in a plenum system is doing the real work while the plenum accomplishes little.

Not to be argumentative, but I'd be interested to know what you have to back this up about the depth of the sandbed. I wonder how one would measure the O2 content in a sand bed at different depths? Perhaps an embedded probe of some sort?

 

[HoopsGuru]

To add a third opinion into the mix there is no way to call any depth "optimal" because it will vary greatly depending on different factors in the tank including waterflow, etc. One tank could effectively get the anaerobic zone with 3" of sand while another tank may require much more.

 

[mojoreef]

DSB and plenums are very different to each other. A DSB is very fine sand set in the tank from depths of 1 inch to whatever you want. It is a system slewed for the population of bacteria and acts as a recycling center with no export beyond nitrogen (according to the experts, toonan, dr. ron, S. gamble).
A plenums main problem in the hobby is that most folks dont set them up right. A plenum is supposed to have grains that are the equivilant to 4 to 5 times the size of CC. With a plenum being completely set back off the glass to not allow the penetration of light.
The biggist difference in the 2 systems is that in a plenum with the coarsness of the grain and good water flow will keep the substraight areobic and thus well oxygenated. This allows for good nitrification. Below the plenum is the are of anaerobic. This area id devoid of oxygen and is where denitrification occurs, also due to its low PH you will get good remineralisation. (bufferin compacity).
With the DSB its tiny grain size allows for greater surface area and thus more bacterial population. Also because of this size grain the anaerobic zone is much closer to the surface (1/2 inch down according to Rob Toonan). This makes for a smaller nitrification zone and a larger denitrification zone.
Both systems have thier pros and cons, but are still recyclers (they create bacterial biochemical cycles) and do not export beyond nitrogen based waste.
The plenum I would have to say is a high energy system (mainly because its grain size makes it less likely to get suspended) and a DSB is a lower energy system (closer to that of a lagoon/swamp and so on.

Logan a way to measure o2 is easy for any system (dsb/plenum) you can simply look at the side you the bed and look for the line. Thiser will be a defined line in the sand layers (sometimes it is darker in appearence or black). this line is the change in zone between areobic and anaerobic, or oxygenated and non oxygenated.

To add a third opinion into the mix there is no way to call any depth "optimal" because it will vary greatly depending on different factors in the tank including waterflow, etc. One tank could effectively get the anaerobic zone with 3" of sand while another tank may require much more.

Agreed totally. An anaerobic zone can occur on the surface even (inside a lump of detritus). A DSB is not a static thing it is in a constant state of flux. With bacterial and algal population increasing and decressing as the food source goes up or down. Acording to Rob Toonan he feels that the anaerobic zone on most hobist tanks occurs around a 1/2 inch down.

Mike

 

[Aquariareview]

secret to DSB

This is a 220 with a 5 year old DSB (between 8 - 10 inch) It has 0 levels of everything. The secret is a lot of critters.

Nassarius vibex snails
These little "zombies" are the most efficient and safest scavenger to use in a reef aquarium. They eat excess food and fish waste to keep your substrate fresh and clean.

Florida Cerith Snails
Cerith snails do a very wonderful thing. Not only do they eat algae!...and detris...but they also eat cyanobacteria! They are long and attractive.

Bubble Snail
This snail is an excellent snail to get to clean up diatoms. The Bubble snail will cover itself with sand and feed on Diatoms while it travels along the substrate.

Most experienced reefkeepers strongly believe in the beneficial effects of bristle worms on the sand bed (see, for example, http://www.ipsf.com/bristleworms.html I hold the view that bristle worms and other sand bed scavengers are vitally important components of reef ecosystems, both captive and wild.

Spaghetti Worms
The common name of these annelids from the family Terrebellidae. These highly active worms have bright red buccal tentacles which extend out over the sand bed to gather suitably sized particulate materials, which they "lasso" by tentacular contraction. It's fascinating to watch, and it sure beats vacuuming your sand bed. Here's a bonus: you can count on these worms to reproduce in your tank because they have direct development (no planktonic stage).

The Two Spot Goby
Also referred to as the Twinspot Goby, Signal Goby, or Crabeye Goby. The head and body are white splattered with orange markings. Its erect dorsal fins are distinctly marked by eyespots.

Usually the Two Spot Goby feeds off the bottom sifting through the sand for food.

 

[Guest]

Beautiful tank!

 

[wseaton]

Not to be argumentative, but I'd be interested to know what you have to back this up about the depth of the sandbed.

I can't, and as far as I know there's been no real side by side study on the issue other than some quasi quantified extrapolation. Basically it's common sense that you really can't have a sand bed too deep, but it's possible to have them too shallow, and that the denser the packing of substrate the shallower the bed can be. Otherwise, I'm with the growing crowd that insists the true optimum depth is not as deep as we previously believed.

The only real way to bring this to a conclusion would be to set up identically stocked tanks with 1", 3" and 6" sandbeds, and then plot waste products over about a year from each tank *without* using a skimmer. We could then argue to our hearts content about what to stock the tanks with and lighting 8)

I'm at a loss though as to what's worse; UGFs, or cannister filters sold with 'bio beds'.

 

[loganj]

I can see your line of reasoning and, you're right, it does make sense. It would take some $$ to do an experiment like that though...rules me out.
I'd have to say the UGF due to the fact that the canister is easier to remove.

 

[mojoreef]

here is a few for ya

http://reefcentral.com/forums/showthread.php?s=&postid=1941608#post1941608

Mike