Does chlorine affect my fish when I use tapwater for water changes?
Chlorinated tapwater is safe for human consumption, but highly toxic for fish. Chlorine is usually added to Municipal water at a concentration of 0.5 to 3.0 ppm (parts per million). Although this seems to be such a small amount, fish are very sensitive to chlorine and concentrations of as little as 0.05ppm are deadly. Larger fish are far more sensitive than smaller fish and are affected by smaller concentrations. Chlorine not only affects the gills of the fish but it also kills the nitrifying bacteria in the biofilter. The resultant spikes of ammonia and nitrite together with the initial damage done to the fish results in the death of the fish 3-5 days after introducing chlorine into the system.
