yes DSB does help in lowering nitrates. jan kasi nakatira yung mga bacteria that help in nitrogen cycle. in fact, almost all reefers here in RP put DSB in their sumps. others DSB + LR in their sump, yung iba DSB + chateo in their sump.
kung mag DSB ka, use really fine sand, wag yung coarse. finer sand lowers nitrates better than coarse sand.




