Deep Sand Bed Questions

[Ping]

Sugar fine sand is purported to be the best sized grain for a DSB and is what I use for DSB’s. A depth greater than 4 inches would be better as the idea is to have a completely anaerobic layer at the bottom of the sand bed. Along with denitrification, the sand will very slowly dissolve under these anaerobic conditions and get shallower with time, providing very minor supplementation of beneficial elements. Therefore, the deeper the bed is when initially setting up a DSB, the better.

Some potential problems with a DSB in the display: The rock work may become unstable over time because of the dissolution of the aragonite. Detritus may build up in areas not receiving enough current. Aquarists have a tendency to put critters in the tank that are detrimental to the DSB as they consume the beneficial sand bed life forms that are slowly stirring the sand bed and turning detritus into inorganic insoluble elements. As well as the inclusion of critters that rapidly disturb the layers of the sand bed, eliminating some of the sand beds denitrification benefits. All of these potential pitfalls can be overcome if the Marine Aquarium System is properly planned and these factors are adjusted for.

Each aquarist setting up a DSB must consider the expectations of the DSB. I believe the only reason a DSB should be placed in the display tank is to support animals that require a well established DSB in order to thrive, such as sand sifting gobies and cucumbers. Most systems with live rock, strong current, and a protein skimmer do not require a DSB for denitrification unless the closed aquarium system has too high of a bio-load e.g. too many fish.

[Troutmasters02]

Thanks for the info Peter. I have a DSB in my refug and I am wondering if there is an ideal range of flow over the sandbed? Is there such a thing as too much flow over a deep sand bed which would prevent the anaerobic layer from doing its job?

[JimD]

Enough flow is when the detritus is suspended, too much flow is when the sand is suspended...

[Ping]

Here is where a DSB gets convoluted, if the DSB is located in a refugium, much gentler water flow will preserve their productivity (Sprung 2005) and personal experience. One reason why this works is there is nothing to interfere with the current causing dead zones and the large pieces of waste have been broken up by the time it gets into the refugium. I use a MJ 1200 in a 55g DSB refugium. No rocks and only a few Caulerpa Prolifera.

Reef Crest currents are aimed at preventing dead zones, keeping the pores of the rock open, and removing the wastes from coral. Attempting to mimic the tremendous energy of the ocean.

[NeptunesGhost]

Enough flow is when the detritus is suspended, too much flow is when the sand is suspended...

Well said

[Troutmasters02]

Here is where a DSB gets convoluted, if the DSB is located in a refugium, much gentler water flow will preserve their productivity (Sprung 2005) and personal experience. One reason why this works is there is nothing to interfere with the current causing dead zones and the large pieces of waste have been broken up by the time it gets into the refugium. I use a MJ 1200 in a 55g DSB refugium. No rocks and only a few Caulerpa Prolifera.

Reef Crest currents are aimed at preventing dead zones, keeping the pores of the rock open, and removing the waists from coral. Attempting to mimic the tremendous energy of the ocean.

Makes sense, thanks for that.

[gjuarez]

This has been very well explained by Ping. Anaerobic bacteria grows where there is very little oxygen, the anoxic zone. That is why a DSB is required to be deep. Earlier it was mentioned that the size of the grain doesnt matter, in my opinion it does. That is why sugar fine sand is recomended, because the grains are so small and tighly pressed together that they do a better job at blocking oxygen into the dsb. Normally a deeper sand bed when grains are larger.

DSB work, they are great in my opinion. Just like Ping mentions, I also only recomended only if it is required for some critters. In the earlier days, the days before skimmers, you couldnt go without one as it was the main source of nutrient export. Thanks to skimmers, more often than not we can afford to go without one. Increase the flow, eliminate dead zones, and turn up the skimmer is the most popular way these days.

BTW, live rock is also great for establishing anaerobic bacteria. It grows very deep inside the rock. The great thing is that it also has alot of surface area where aerobic bacteria grows.