How deep?Problems with?

I was under the impression that grain size makes a difference in the efficacy of a DSB. I have a 6" DSB in my sump/fuge with a couple nassarius snails. When I put it together I put small grained aragonite (not sure the size in mm)--basically the grain size one size up from sand. But since I have read a few articles expressing the notion that different depths of DSB require different grain sizes.

In general, I think the DSB is really a secondary bio-filter as so much denitrification happens deep inside the LR.

 

i know the grain size matters when doing a plenum*. but i would agree that you should be look at your sand bed to do most your work. thats what the live rock is there for, but it could help to reduce the amount of live rock you need to work with in your tank

 

That is something I have never really seen. I know it is not an exact science, but I have never heard any type of how much dentrification takes place in LR or DSB. I realize it does, I've just never seen any type of info that a DSB of around so deep, will reduce nitates this much per sqare foot.

I want to do a fuge with a DSB, but don't see how it will be that usefull for reducing nitrates. I'm really doing it to support a good pod poulation and associated critters.

 

Hi guys, stumbled onto this post, and thought it deserved some comments:

Deepsand beds need to age and cycle to build up levels of anaerobic bacteria in much the same way that liverock and biofilters need to (I remember it being more than a couple of days).

Size, depth, grain size, water flow, amount of O2 in the water, critters and many other factors will affect how much nitrate a sand bed will remove, so no it's not anything near an exact science.

The article How Sandbeds REALLY Work by Ronald L. Shimek, Ph.D. - Reefkeeping.com previously mentioned does not satisfy my fears of issues in the long term.

A quote from the end of that article, talking about the bottom of your deep sandbed, "Here, bacteria and chemistry combine to produce conditions that result in the precipitation of many toxic heavy metals such as sulphide and iron hydroxide minerals. (Pincher, et al., 1999, 2000) Such materials accumulate in the tank with time, but as long as these sediments remain anoxic, those poisons are locked there and can be considered "safe.""

This says to me that the practice of removing all of your sand and replacing it every year or so is a good idea, especially considering the anecdotal evidence of long term problems with deep sandbeds.