DSB in refugium? With or without mud?

[ChrisC1029]

I am planning on adding a refugium to my system. Currently have a 105 gallon display tank with sump. The refugium will be an old 55 gallon tank I have, pumping water from the sump and spilling back into the display tank by gravity feed. Plan on growing macroalgae and probably xenia for nutrient export.

Questions are:
1. Is there much benefit in putting a 5-6 inch DSB in the refugium, to further decrease nitrates? My display tank only has a 2-3 inch live sand bed.
2. If so, is there much benefit in layering 1-2 inches of "Mineral Mud" or Kent "Biosediment" on top of the oolitic sand (Carib Sea Aragamax Sugar Sized oolite)?

thanks for the help.

[Doug1]

Chris, I got to attend Rob Toonens lecture on sand beds last weekend in Seattle and his opinion is the more fines you can get in the sand bed, the better off you will be in the long run. On the otherhand, you have to let the fines settle into the oolitic sand, wait for biofilm to develop, and use as many cultures as you can from diverse existing sand beds to increase the meofauna count. Given what you want to do, I would think its gonna be OK if you have the patience to let it mature and use a slow flow thru it

[ChrisC1029]

Thanks Doug.
I'll plan on doing it, with at least some "mud" on top of the oolitic sand to get some smaller grain size. I've read on the boards that some people believe a DSB in a refugium is not as efficient as a DSB in the display tank, but I figure that even if it doesn't help much, its not going to hurt anything either.

[Doug1]

I have heard pros and cons re: DSB in fuge vs N reduction, I think a lot depends on the size of the fuge vs display tank , water velocity and a host of other issues
at the very least it should host a wider variety of organisms that contribute to N reduction and olanktor production