deep sand bed

[dmatt56]

Hello Everyone,

 

I liked the idea of adding a deep sand bed - or at least another inch or two of sand to help control nitrates. I currently have 1 - 2.5 inches of sand. What's the best approach of adding sand and not creating a new cycle? What sand is recommended? I added 20 lbs of Nature's Ocean Bio-Activ Live Aragonite Reef Sand after I purchased the tank, but I'm not sure where it went. Is there any benefit to creating deep areas or should I keep the depth constant throughout?

 

Thanks,

 

Matt

[ryanls5]

Hello Matt, if it were me I would add the DSB to the sump with new sand and seed it..but I don't know what you already have cooking there. How long have you had your tank set up? Do you have a sump? Any livestock? Sorry if you have already posted elsewhere with what you got just trying to help you out. I am pretty sure you can add a DSB to your sump and then seed it without much of a cycle if you add it to your sump/refugium, but I could be wrong but that would be my course of action. I wouldn't add it to the display as IMHO it could make nitrate gas bombs and leech out...could be wrong there too but I'll let these guys chime in

[Happyfeet]

I'm not an expert on the subject, but I've done a good amount of reading. From what I understand a DSB doesn't reduce nitrates or anything, it just absorbs more. The problem is, and after my reading I haven't found anyone that didn't escape this fate, the DSB reaches critical mass can't hold anymore and starts to release back into the water. Granted it's only a little bit that

[Origami]

From what I understand a DSB doesn't reduce nitrates or anything, it just absorbs more.

 

This is incorrect according to much of the common literature. Sand is not "absorbent" as you would imply.

 

I'll try to summarize what I know on the matter here, but there's much available on the net and in other places that's easy enough to find.

 

Here's one article that get's a little technical from Ron Shimek: http://reefkeeping.com/issues/2003-06/rs/feature/index.php

 

Here's another, less technical: http://reefkeeping.com/issues/2008-05/newbie/index.php

 

DSB's, according to the literature, provide aerobic (oxygenated), hypoxic(low oxygen), and (if deep enough) anoxic (no oxygen) zones. DSB's tend to be built up of relatively fine grained (2mm or less) sand, that provide reduced movement of water through the substrate. This allows certain bacteria that are adapted to these zones to colonize those zones in sufficient numbers to complete the nitrate cycle.

 

In the upper layers, it is thought that nitrosomonas bacteria consume organic waste in the form of ammonia in the oxygenated environment, converting it to nitrite (NO2-) and then to nitrate (NO3-). By passive diffusion into the lower layers, these nitrates are reduced to nitrogen gas (N2) by nitrobacter bacteria, which can strip the oxygen off of the nitrate ion, living within the hypoxic zone. (The process is identical to what is thought to happen in live rock.) Thus, all of these products of decomposition (ammonia, nitrites and nitrates) are reduced (converted actually) and are not "absorbed."

 

If the sand bed gets too deep, an anoxic zone can be developed. Without oxygen, bacteria at in this region will consume sulfur (closely related to oxygen on the periodic table) in the form of sulfites (SO3--) to get their oxygen, leaving behind toxic (and smelly) hydrogen sulfide (H2S). It's thought that these are the "black" zones that you can find in some DSB's when they are broken down at the end of an aquarium's service. If released (through agitation of the deepest layers of a too-deep sand bed for example), hydrogen sulfide can cause a lot of problems for your aquarium.

 

Besides hydrogen sulfide in a sand bed that is too deep, using a sand grain who's size is too large for a deep sand bed can also cause problems. If too coarse, a sand bed can allow detritus to accumulate deeply into the bed and beyond the reach of normal, benthic organisms that live in the upper (aerobic) region of the DSB. As this detritus breaks down, it produces nitrates at a rate that exceed the capacity of the bacteria in the hypoxic zone and can become a nitrate factory.

 

Summarizing: A "proper" deep sand bed is typically 4-6 inches deep and composed of relatively fine grained sand. It should support and be populated with a variety of benthic organisms such as worms, snails, sea stars, and the such to keep the upper strata clear of detritus. It is a useful device to complete the nitrogen cycle in your aquarium. If too deep, anoxic pockets can develop which can harbor toxic hydrogen sulfide. If too coarse, detritus can settle and accumulate causing excessive nitrates to form.

 

Want to read more on nitrate in the reef aquarium? Here's a good article by Randy Holmes-Farley. http://www.advancedaquarist.com/issues/august2003/chem.htm

Edited October 14, 2009 by Origami2547

[zygote2k]

The secret to the success of my skimmerless system is the DSB. It's about 4" deep and is made of Aragamax sand. When I placed it online, it took the N03 down from 40ppm to less than 5ppm in a little over a month. Mine is completely covered with eggcrate and the return pump sits on top. It is in my sump container and is completely dark to prevent unwanted organisms from growing there. It has been in operation for about a year and a half. I reccommend a DSB to anyone who wishes to remove N03 the natural way.

[Vader]

I started out with a 3" sand bed and I never had an issue with NO3 in my tank. The last time I measured for it, it was less than .5 ppm. I have no idea why I don't and others do, but I'm not changing anything I'm doing.