A paramount factor in the proper maintenance of an aquarium is the dilution of accumulated waste by scheduled water changes. This requires the removal of chlorine or chloramine or both from the new water. With the advent of chloramine, thiosulfate has proven inadequate, causing the release of ammonia. At acid or neutral pH, this is not of serious consequence. However, at alkaline pH it can be devastating, particularly if the tap water is heavily treated with chloramines.