Deep sand bed, how deep is too deep?

DarkTang · Nov 14, 2014

I have a 90 gallon refugium that is 36Lx19Wx30H. It's a tall acrylic tank and I was wondering what would be too deep making it not beneficial to use?

Mike J. · Nov 14, 2014

I don't think a DSB can be too deep. But, generally 5 - 12 inches is what's used.

DarkTang · Nov 14, 2014

Ok sweet it's going to be a 300 gallon total system. How deep should I make the remote sand bed? This refugium drains right into 135g sump and pumps back into 75g dt

rayn · Nov 14, 2014

Just did the exact same thing. My DSB is about at the 4" mark. Remember that after a few years you will want to start changing it out bit by bit. Do deep and it may be more pain then anything.

DarkTang · Nov 14, 2014

rayn said:
Just did the exact same thing. My DSB is about at the 4" mark. Remember that after a few years you will want to start changing it out bit by bit. Do deep and it may be more pain then anything.

Why more pain than anything?

rayn · Nov 14, 2014

You go with a 6-10 inch DSB and then try to change it and you may have sand slides. Or maybe your macro algae will come unrooted. I am just trying to think ahead to maintenance aspects of it. If it should calcify then you could disturb more then you want and create a nitrate spike.

Just thinking here.

DarkTang · Nov 14, 2014

Ah ok, what's your setup like? What's the total water volume? What macro algae are you planning to put there?

rayn · Nov 14, 2014

120 display, 40 remote fuge, 40 sump. Just finished cycling so nothing in yet. Planning a bunch of macros, of varying colors, for the fuge. Planning a sps dominate tank and it is bare bottom. If the DSB becomes a issue I will just disconnect it.

DarkTang · Nov 14, 2014

That's the same setup as mine! SPS dom and bare bottom! I'm planning to put 300 lbs of rocks in the sump and minimum rocks in dt

Randy Holmes-Farley · Nov 14, 2014

How deep a sand bed needs to be to allow denitrification depends on how coarse the material is.

Finer sediments become anoxic with less depth because diffusion and flow of water into and through them is lessened.

DarkTang · Nov 14, 2014

I have really fine sand

Randy Holmes-Farley · Nov 14, 2014

Really fine sand, IMO, needn't be more than a few inches.

My rational is that I had a deep sand bed for several years using fine oolitic aragonite. It was about 8" deep. When I took it down (because I thought it wasn't doing much that was useful), the sand that was more than a few inches down seemed totally pristine, as if nothing was going on there. No creatures, no organic matter, no discoloration of any sort, no bubbles. So I think nearly all fot he useful biological activity was happening in the top inch or two or three.