deep sand bed have it or not?

Hi,

I've done 2", that was a nano. For my 100g I did a 3". It was my thinking at the time that there was more exposed surface in the nano - and I wanted to "try going less." It worked fine. But I had a lot more flow and bioload in the big tank, plus a higher percentage of the total footprint was covered with l/r. At any rate, both worked fine in processing nitrates. I think with the finest-sized sand the 2" will do you well. The bigger diameter the grains, the deeper the DSB needs to be, so you don't get oxygen cycling to the depth where the nitrates need to be converted. I know some people have done -2" oolitic, so I don't know what the absolute minimum would be. Check out the sandbed swap article if you are tossing that coral sand in favor. I think you're going to be very pleased with your end result. I think the reason I favor the 3" in a larger system is just because I know I'm going to be "driving down" the stacked l/r and contacting the bottom of the tank. That's one place I like to "keep my rocks off!" :D Seriously, though - in a 10G nano your not going to be putting poundage in there to contact the bottom of the glass tank. When it comes to putting the eggcrate in, that's an excellent way to keep rocks from contacting the bottom - and if I could use that "ground frame" just under the rocks I think that is a great concept. But bear in mind the grid thickness; wherever you have plastic, you do not have any bacteria being processed. So I wouldn't want to cover my entire tank bottom with it, where there's no l/r to support. The common thought would be to just measure a rectangular bottom, cut to size - and drop in for the foundation. Maybe it makes no difference if you have the entire bottom covered, but another reason I've gone with just the sand is so that I can manually "turn" small portions of the sandbed at a time over the years. Way back when people started talking about "toxic sandbeds" that just seemed like the logical thing to do - and I never had a sandbed blow up on me - whether the "turning" helped or not. You do know with just that DSB you can get rid of all your mechanical toys, right? ;) I think it was my razor caulerpa that really helped play a factor in helping to keep my systems "polished."

Anyway, I've never seen a large system fail with a 3" DSB because it wasn't processing nitrates. The largest system I've run a 2" in was a 55g. But keep in mind - that's just me. If just one person has run a 1000G tank with a 2" oolitic bed - you have your answer: it can be done at that size. I haven't been around the boards for awhile, but I think it's going to be awesome seeing where people have gone in this direction, or if there hasn't been much change from the "standard 4" at the (gulp)... turn of the century. :eek:
 
Eggcrate is referred to as that plastic "grid" typical of what you might find in some lighting fixtures. That still might not explain it well, so just imagine a sheet of hard plastic about 1/4 - 1/2" thick. Now, cut out equally spaced squares leaving a thin space between each of them. You would be left with a "grid" shaped piece of plastic. Placed in the bottom of your tank, rocks would rest on that and not your glass bottom. Not being a fan of glass tanks, you don't need to worry about plexi. But drop a piece of rock on that glass bottom and you stand a good chance of breaking it. We once had a big Mag pump slip when trying to remove it from a glass sump - that broke and caused a nasty headache. Some of that eggcrate would have been a super insurance policy, in that situation. I since went to using plexi for sumps, as well. And yes, people have used 2" in their tanks. Like I said earlier, though - that gets you toward the minimum. You will actually see the "layers" of where your sandbed is processing. I think that's when people figured out they didn't need 5". I will stress, again, that the size of your sand is important. I'm not sure if you're familiar, but I've seen "reef sand" sold which is actually crushed coral. Forget about processing nitrates in that stuff. When people talk about "oolitic" that's commonly referred to as "sugar-sized." Also keep in mind that if you go 2" and have any fish that "sift" or cause a commotion on that sandbed you will be bringing oxygenated water into contact with the anaerobic layer - and you will get an oxygen exchange which ruins the whole concept of transforming the nitrates to gas. Most everyone who runs 2" knows this, so bear that in mind.

One of the things that often been of wonder to me is just how a DSB can function with the size of some of the bristleworms I've seen, even at 3". :eek: I mean, I'm not the microbiologist, so I can only wonder about the need to "keep it oxygen free" and then you have a 12" plus-sized bristleworm come plowing through, all the way to the bottom of the tank. :confused: These are great to "sift" and turn the sand, and it just makes me ponder where the limits are... but it does not lend me question the fact that the DSB still functions perfectly. With some of the sizes of worms I've seen, I would think if they started a parade down there, they'd aerate the entire DSB. :eek: But, perhaps in that balance of nature, they do it "just enough." I can only wonder about the process, but I do know the results so I go with it.

If you're going with a DSB in that 400L tank, I'd give myself the added "peace of mind" knowing that a 3" bed will bring. And if your tank is glass - just make sure you don't drive sharp corners into the sand. I always try to use as much flat rock as I can to build my foundation... any pieces that fall while in the water won't drive through a 3" sandbed. I see you're running a very think layer of coral sand in your present system. I do know you'll be getting no nitrate conversion with that depth. You might be thinking that 2" will be a big difference, but again - with oolitic I wouldn't go any less. HTH! :)
 
Hi
Thanks once again FISH WHISPER for that advice. I have started a 2" DSB and have put eggcrate all in the bottom of my tank. The sand i used is from the great barrier reef and is super super fine, its fanastic stuff. I mixed a bit of coral sand through it to hopefully stop the sand from becoming compact. I also put 3" of shell grite in my trickle system to raise my carbonate hardness because this super fine sand wont do that. I am now planning on buying a wrasse to flip over the top layer of the DSB. I also have put a nitrate remover (which i have made) online and i will see if that works.

Thanks again FISH WHISPER for your great advance, You prodived me with alot of information that has and will come in very handy.
 
No problem, glad to help.

One other thing - you mentioned your sandbed becoming "compact". You can "turn" it manually by getting along wooden dowel and just "tilling" one small area at a time. You wouldn't do the entire DSB, but just a little bit at a time - as necessary if it does start clumping. Another useful "tool" that can be had are the long clear tubes usually housing thin flourescent bulbs. It's nothing more than packaging for the bulb, but I found the half-inch diameter perfect for target feeding, and that's what I used to manually "sift" through small sections of the DSB over the course of time. It's sort of a "multipurpose" freebie tool and for me it's tops for target feeding corals, fish, etc. You can see the food, and fish won't be able to get at it. Depending on what you're "sinking" down the tube, though - it can sometimes be a pain. Why? Because some food sort of "floats" at the surface until it becomes saturated and then starts to sink. Anyway, you mentioned the sandbed compacting and I find this to be a useful device with a few nifty purposes. I actually used to blow down the tube to create a manual "bubble" at the bottom of the sandbed. That would ensure the release/exchange of gasses. Obviously since nobody does this it's not necessary, but I never worried about my DSB "imploding" or crashing. Hey, HTH! :)
 
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