Partial water changes are done to maintain the
water quality of
aquariums. The amount removed must be limited in order to maintain an adequate amount of the helpful
bacteria in the
tank for maintaining the
nitrogen cycle. Large water changes also make larger changes in the
pH and/or
temperature of the water more likely. Sudden changes in the quality of the water may be stressful to the fish and can cause disease and death.
Old water is removed while cleaning the gravel (if gravel
is being used) with a
gravel vacuum. The new water must be
dechlorinated prior to being placed in the
aquarium. Efforts are usually made to make the
temperature of the water added identical to the temperature of the water in the tank. At times slightly
cooler water is used to imitate a
rainstorm. This induces breeding behavior in some fish. Larger than usual partial water changes may also be done to induce breeding behavior in somefish ... "Flash flood or rainy season, better breed quick!" said one fish to the other...
If the
tank is a
saltwater tank the
saline ratio is also matched. At times
chemicals are used to match the
pH of the new water to the older
water. If you dislike adding excessive chemicals to your
tank and if your fish require a pH either more acid or more alkaline than your tap water then smaller and more frequent partial water changes are even more important.