I have used FBF (sand filters) with great success on my FW tanks. My ammonia levels used to shoot through the roof after feeding despite my WD, two canisters and a HOB filter. My water stabilized within a week or so after I added the FBF. My question is would the FBF be of any special benefit to a SW tank ? From what I've read, many seem to discourage it's use because of it's efficiency. It seems that it takes the denitrification process away from the LR and LS and puts in the filter itself. Anybody use them ? I was thinking of building a DIY sand filter in my sump. :scratch: