Failure to change water frequently allows the accumulation of pollutants that will affect fish health and growth. So why do we have to change water? Basically for a few reasons: 1) supply fresh water to the fishes 2) removal of excess waste or food 3) removal of Nitrate and any presence of chemical 4) finally, water changes replenish elements and minerals in the water needed to maintain a healthy environment in one of the message posted by ranchugirl, it was mentioned that frequent water ch