how deep of a sand bed for a fuge

[AquaJohn]

How deep should a sand bed be in a fuge about 13X13x14 deep

[FarmerTy]

Oh, I'd be curious to this answer myself. Currently running with no sand in the fuge but the system has been up and flawless for the past 4 months. Wanted to see if it was a good idea to add a DSB in the fuge.

-Ty

[Gonzobob]

I run a DSB on 1 of my fuges (don't on my nanos due to space considerations) and will on the new tank as well. Sand depth around 5-6"

[+Daniel]

I run 0" and actively try to remove sand and detritus from my sump and fuge.

[Rgwiz11]

From what I've read if you want a DSB to form an anaerobic zone, you need a minimum of 4", but no more than 8", otherwise you run the risk of your bacteria creating that nasty hydrogen sulfide gas

[offroadodge]

mine is 4" with about the same dimensons. 15lbs of live rock, 5 mangroves, and chaeto

[subsea]

To be functional as a de-nitrate filter the grain size is the determining factor for the depth of the sand bed. Even though it is not popular on this site, I operate a Jaubert plenumn with CaribSea crushed coral (2-5mm grain size). This grain size requires a minimum of 4" with many commercial facilities going more than 12". The hydrogen sulfide that was referenced is a common molecule in all deep sand beds. If you go to a technical reference of the "faculative zone", you will see the complex reduction chemistry going on in this depleted oxygen zone. The reason for the large grain size is that the oxygen gradiant is spread out over more depth and thus more faculative bacteria. The first couple of inches of sand is an oxygen rich enviroment. Thus oxidation chemistry occurs in which ammonia is turned to nitrite and then nitrite is turned into nitrate. Each of these processes uses a different bacteria.

The typical deep sand bed uses .5-1mm grain size and is less than 4". For some people, 4" is too much to give up in the display tank. For this reason and many more, the refugium has come into dominance in reef aquariums. I like a DSB with an algae filter. I choose several types of Caulerpa because the fish love to eat it. If you don't have fish that eat it, then through it away as a nutriant export technique. Because I do not use a protein skimmer, this is the main nutriant export method in my system.

Patrick