Deep Sand Bed -- Anatomy & Terminology

[Amphiprion1]

Below the typical recommended surface area @ 18" x 18". Seems to be holding its own, however, and it is approaching 1 year at its current configuration.

[dasstheboss]

I have a general question about Deep Sand Beds. Based on your approach to the filtration, would this mean that in a tank of around 220G (72 x 24 x 30) I can make a sand-bed of about 6" deep all through the tank - I initially wanted a 180G but thinking about a DSB makes me want to try getting the extra 6" in height for sand.

 

This way, I would have a deep sand bed that can house worms and other critters I can slowly populate the tank with while also helping me lower the need for water changes. I can supplement for other trace elements with dosing and a calcium reactor will take care of alkalinity/calcium. Does this seem doable? If so, then it would help a lot lowering the need for water changes and I think the large area for the sand bed can certainly work out well too.

[Whys]

...a sand-bed of about 6" deep all through the tank...

 

The ideal depth for your sand bed can depend on a number of factors. The most obvious are grain size and water flow.

 

There is no predetermined formula, but six inches is probably pushing it for most setups. I wouldn't even try six inches with oolite unless I was putting it in some kind of HOB refugium I could easily remove. And while a larger grain size will allow more water flow, and thus oxygen, to penetrate deeper into the substrate, you don't want to use too large of a grain size either, because it'll be more likely to trap detritus. Long story short, I personally don't recommend anything deeper than 5 inches, and even that can be too deep if the substrate suffers from too much compaction.

 

The bicarbonate sands we most often use in our reef tanks are known for their ability to help buffer the water, but they do so at a cost. This is especially true with deep sand beds. Eventually enough material dissolves into the water column such that the sand begins to compact. In sever cases, the substrate can actually hard-pan or "brick". Of course, that would suggest a lack of agitation as well.

 

Your goal is to provide just the right amount of flow to just the right depth of the substrate, no less, no more. There is a whole lot of nuance to consider and even more conjecture to digest. There is no script to follow. You have to go on instinct as much as science, and don't screw up or it all goes bad. It really is just that simple.

 

Having said that, if you follow the general rules of thumb, I think most people will find that there is a fairly large margin for error. Just be aware. Filling a huge tank with a full six inches of sand will not only be enormously heavy, but then what do you do if the sand goes bad?

[dasstheboss]

You have a great point in the 6" being too deep and not being able to fix it if things go wrong. What do you say about using oolite sand at about 4"? There would be a lot of critters in the sand to keep it oxygenated. I will try to do more research on grain size to find which would be the best for me. Thanks for the help.

[Whys]

You have a great point in the 6" being too deep and not being able to fix it if things go wrong. What do you say about using oolite sand at about 4"? There would be a lot of critters in the sand to keep it oxygenated. I will try to do more research on grain size to find which would be the best for me. Thanks for the help.

 

I think 4 inches would be close to ideal. I went with 5 inches because I use OceanDirect's Original Grade, which contains a fair amount of larger grains. 4 years old and still going strong, but I also have a lot of water flow at sand bed level. I feel this has played an important role.

 

Best way to avoid compaction is keep your water levels on target so the sand doesn't have to buffer it, and lots of small worms keep it both gently agitated and clean.

 

It would be pretty epic to see one on the scale your thinking. Do post a photo!

[mattclark82]

Your diagrams explain it, but sometime I think there can be a little bit confusion. We want anoxic conditions by definition, where DO is around 0.2 ppm or less, and where there is bound oxygen, in our focus, as NO3/NO2.

Anaerobic conditions are a problem, where there is low DO as well as low NOx, where a whole bunch of bogus stuff can happen, reducing SOx to H2S. Black areas or smell could br an indicator. In waste water plants, anaerobic zones purposly cause major expelling of PO4 from the breaking down of polyphosphate chains bound and built in the cellular mass. I always wondered to what extent this happens in araerobic conditions in tanks.

I guess my point is there is a differance between anoxic and anaerobic conditions, and the terms shouldn't be interchangable, and can help explain the line where a DSB is good and where is can be a problem,or maybe I am just being too crazy.

 

I agree that the terms can mean very different thigs depending on the field.

[mattclark82]

Or maybe my wastewater terms are different in this sense. I just know that the two terms anaerobic, and anoxic are often interchanged, but in the ww industry mean very different things.

[Whys]

Your diagrams explain it, but I guess my point is there is a differance between anoxic and anaerobic conditions, and the terms shouldn't be interchangable, and can help explain the line where a DSB is good and where is can be a problem,or maybe I am just being too crazy.

 

The terms aren't treated as interchangeable. Their side-by-side appearance in the diagram is explained in the article.

 

You are using the terminology used by environmental scientists. The diagram gives preference to the actual dictionary terms, not the borrowed terms you are using. Anoxic means no oxygen and anaerobic isn't even a chemical state, but rather a biological process. I do understand the reasoning among environmental scientists for borrowing these terms against their dictionary definitions, but it's confusing. That's why I recommend speaking in terms of "nitrifying", "denitrifying", and "reducing" bacteria. Of course, you can substitute "facultative" for denitrifying, as you might prefer.

[11GTCS]

Would you recommend a DSB for a pico? It's a small footprint, so I don't know if that would affect anything. Also, all of those organisms come with LS and LR yes? I don't have to stock them somehow do I?

[mattclark82]

Then what terms would you use to differantiate between:

1) the condition of NOx and low DO (desirable). Hypoxic?

2)and the condition of low DO, low to zero NOx, where bacteria will reduce sulfates to H2S and other nasty reactions (undesirable). Anoxic?

I might just be getting hung up on the exchange terms. I see a lot of threads where people mix/mash anoxic, anaerobic, septic, etc when refering to "black stinky zones" of substrate. I think your definitions above could help people confusing the differance between a well working DSB, and a sandbed which could go bad and sour peoples ideas of DSB.

[Amphiprion1]

Then what terms would you use to differantiate between:

1) the condition of NOx and low DO (desirable). Hypoxic?

2)and the condition of low DO, low to zero NOx, where bacteria will reduce sulfates to H2S and other nasty reactions (undesirable). Anoxic?

I might just be getting hung up on the exchange terms. I see a lot of threads where people mix/mash anoxic, anaerobic, septic, etc when refering to "black stinky zones" of substrate. I think your definitions above could help people confusing the differance between a well working DSB, and a sandbed which could go bad and sour peoples ideas of DSB.

 

The terms themselves would be independent of nitrogen concentration, but are otherwise correct. That doesn't mean those situations don't occur, obviously. I'm not familiar with wastewater terminology, but this is the case in most biological fields.

[Whys]

Would you recommend a DSB for a pico? It's a small footprint, so I don't know if that would affect anything. Also, all of those organisms come with LS and LR yes? I don't have to stock them somehow do I?

 

No. But that doesn't mean it can't be done.

 

Yes, OceanDirect live sand and Fiji live rock seem to come with everything you really need. The key is to cultivate the benthics properly.

 

As promised, my own DSB at 3.5 years old.

 

[11GTCS]

No. But that doesn't mean it can't be done.

 

Yes, OceanDirect live sand and Fiji live rock seem to come with everything you really need. The key is to cultivate the benthics properly.

 

As promised, my own DSB at 3.5 years old.

 

I want to use it in a Dwarf Sea Horse Tank... I can't put LR that's fairly fresh in because the hitchhikers can kill the poor things. But I put a DSB anyway with some rock from my other tank... We will see what happens! Its a new tank so if anything I'll just have to take it out if the levels seem to not work out.

[Whys]

I want to use it in a Dwarf Sea Horse Tank... I can't put LR that's fairly fresh in because the hitchhikers can kill the poor things. But I put a DSB anyway with some rock from my other tank... We will see what happens! Its a new tank so if anything I'll just have to take it out if the levels seem to not work out.

 

Yeah, hydroids, watch out for those.

 

I'm currently trying a DSB on my kreisel, no live rock. The only things in there are either microscopic stuff that come in on the breeder water, or hitched a ride and survived on some chaeto dipped in coralRx. I have seen one vermetid snail, but those don't do much for the sand bed. I'm considering trying to put some spionid worms in there, but the sand is sugar-fine quartz, and at 3.5 inches, I'm not certain it's a functional DSB. I think it might just be three and a half inches of nitrification. It's in a HOB refugium.

[11GTCS]

Yeah, hydroids, watch out for those.

 

I'm currently trying a DSB on my kreisel, no live rock. The only things in there are either microscopic stuff that come in on the breeder water, or hitched a ride and survived on some chaeto dipped in coralRx. I have seen one vermetid snail, but those don't do much for the sand bed. I'm considering trying to put some spionid worms in there, but the sand is sugar-fine quartz, and at 3.5 inches, I'm not certain it's a functional DSB. I think it might just be three and a half inches of nitrification. It's in a HOB refugium.

 

My dad is currently cycling some nice new LR, is there any way I could grab some for the bennies of the bacterial and organisms but keep hydroids out??

[Whys]

Better question... is it even possible to keep hydroids out? Unfortunately, I'm not one to answer that for you, as my experience with it is limited. What I can say is that there seems to be only two solutions to getting rid of them. One only works half the time and the other kills pretty much everything. A functional DSB takes time and if the former solution proves insufficient, the latter will undo your DSB, perhaps permanently, as the treatment residuals will persist indefinitely.

 

I can't help you beyond that except to say that what you are attempting to do is difficult and prone to trouble. Totally worth experimenting.

[11GTCS]

Better question... is it even possible to keep hydroids out? Unfortunately, I'm not one to answer that for you, as my experience with it is limited. What I can say is that there seems to be only two solutions to getting rid of them. One only works half the time and the other kills pretty much everything. A functional DSB takes time and if the former solution proves insufficient, the latter will undo your DSB, perhaps permanently, as the treatment residuals will persist indefinitely.

 

I can't help you beyond that except to say that what you are attempting to do is difficult and prone to trouble. Totally worth experimenting.

 

haha I am gonna go down the Marine Sciences department at my college (UNH, we have a pretty big one) and see if they can help me! I'll just put a piece of the LR in for now I can always just not do seahorses if a microscope confirms em!

[Whys]

...bump...

[fraxinius]

i seem to have at least a partial deep sand bed that has been created by accident..

i only had about 2" of fine aragonite sand when i set up my 10g with no intent of doing dsb...my pistol shrimp and watchman changed all of that...looking back, shoulda got a smaller one but he burrowed all around and thru my 23lbs of lr, displacing a lot of sand with much piled up on the front glass...i have this corner of the tank i was able to move sand into and now have about one fourth of the tank with at least 4" sand in it...looks healthy, just small, tank is doing well..i think the pistol has most of the sand he can move out of the burrows and just does touch ups now, he has been leaving the open deep sand area alone staying among the rocks...i have just 1.5" at front of tank with it sloped higher to back and right corner....have small powerhead blowing lightly thru the lr and gently across the sand.. not perfect, but seems ok for now

[cbandotho]

OK, I have read through this and I am on the fence.

 

I am setting up a 75g and I definitely want a sand bed. I am trying to decide whether or not to go deep or shallow. Are the risks as great if I go with a shallow sandbed? It seems I would sacrifice some of the benefit but would have the aesthetics I want without the risk?

 

What am I missing?

What would you recommend?

[Whys]

i seem to have at least a partial deep sand bed that has been created by accident..

i only had about 2" of fine aragonite sand when i set up my 10g with no intent of doing dsb...my pistol shrimp and watchman changed all of that...looking back, shoulda got a smaller one but he burrowed all around and thru my 23lbs of lr, displacing a lot of sand with much piled up on the front glass...i have this corner of the tank i was able to move sand into and now have about one fourth of the tank with at least 4" sand in it...looks healthy, just small, tank is doing well..i think the pistol has most of the sand he can move out of the burrows and just does touch ups now, he has been leaving the open deep sand area alone staying among the rocks...i have just 1.5" at front of tank with it sloped higher to back and right corner....have small powerhead blowing lightly thru the lr and gently across the sand.. not perfect, but seems ok for now

 

As long as the pistol keeps moving things around, it won't be a functional DSB. The activity delivers too much oxygen to the lower layers. Probably nothing to worry about either, as the pistol will eat any trapped detritus it finds.

 

OK, I have read through this and I am on the fence.

 

I am setting up a 75g and I definitely want a sand bed. I am trying to decide whether or not to go deep or shallow. Are the risks as great if I go with a shallow sandbed? It seems I would sacrifice some of the benefit but would have the aesthetics I want without the risk?

 

What am I missing?

What would you recommend?

Deep sand beds are for those who understand and want them. If you don't feel you have a clear need or desire for one, then I'd recommend exploring something else. There are other means of reducing nitrate.

[cbandotho]

As long as the pistol keeps moving things around, it won't be a functional DSB. The activity delivers too much oxygen to the lower layers. Probably nothing to worry about either, as the pistol will eat any trapped detritus it finds.

 

 

Deep sand beds are for those who understand and want them. If you don't feel you have a clear need or desire for one, then I'd recommend exploring something else. There are other means of reducing nitrate.

 

The benefits make sense to me but I just read your response about the pistol shrimp which I will have in my display. So that probably answers my question.

 

Do you have any source or opinion on maintaining a shallow sandbed?

[fraxinius]

does a dsb in only part of the aquarium provide any benefit??? pistol shrimp has not been into the deep area for 2 months now..i think he is almost to glass in the burrows and out of sand to move..the deep area i have nicknamed the "abyssal plain" it is the most open area with only minor surface activity from nassarius and twin spot..i only disturb the shallow sand areas in front.

[Whys]

The benefits make sense to me but I just read your response about the pistol shrimp which I will have in my display. So that probably answers my question.

Not necessarily. That was in response to an unintended deep section of sand. If you intend a deep sand bed, then it can typically be setup to accommodate a single pistol. I've seen it done before.

 

Do you have any source or opinion on maintaining a shallow sandbed?

Vacuum often.

 

If I weren't doing a DSB, I'd probably go bare bottom. I hate vacuuming.

 

does a dsb in only part of the aquarium provide any benefit??? pistol shrimp has not been into the deep area for 2 months now..i think he is almost to glass in the burrows and out of sand to move..the deep area i have nicknamed the "abyssal plain" it is the most open area with only minor surface activity from nassarius and twin spot..i only disturb the shallow sand areas in front.

If oxygen levels become depleted enough, then denitrification will occur. But if it moves around often, then oxygen levels won't deplete.

[mike c]

Deep sand beds are for those who understand and want them. If you don't feel you have a clear need or desire for one, then I'd recommend exploring something else. There are other means of reducing nitrate.

+1

The pistol will be fine with an inch of sand. No matter how much sand you put in the tank, wheather 1/2" or 1", I believe your should constanty stir and siphon it. Siphon it weekly with water changes, and stir it up every couple days in beetwen. 99% percent of waste export will come from live rock and mechanical filtration. Sand in my opinion is for looks. To be a true sufficient means of waste export, sandbeds have to be pretty darn deep. Deeper than most want to deal with. Also (my opinion, again), sand should be changed out every 8 months to a year.