Sand in sump/refugium

[Myka]

IME, sand will increase the pod population in the fuge, but they may or may not survive the trip back to your tank depending on the pump you use. I would NOT suggest you use very much sand though as DSBs cause more trouble than they're worth imo. If you have a satisfactory amount of high quality live rock in the tank (and sump if you want), then you should not have troubles with denitrification provided you aren't overloading your tank with livestock and/or nutrients.