I use a foam block in an AquaClear 70 on my 55 gallon planted tank, along with two bags of biomax (ceramic pieces) and no carbon. Because of the plant matter I have to rinse out the foam every three weeks or so, and I replace it (by adding a new block above the old one for a few weeks) every 6 months or so when the old block starts to fall apart.
ladycage, the bacteria that live on the foam blocks break down the waste products from the fish and produce nitrate (NO3
). In a freshwater tank NO3
is removed with water changes and is not usually a problem. In saltwater tanks, especially reef tanks, NO3
is very bad for corals and invertebrates and should be maintained at the lowest levels possible (0, ideally). Most saltwater tanks use skimmers to remove NO3
and other waste products, and don't use foam, biomax or bio balls in their filters as they produce too much NO3