How Many Times a Week Should I Change Water in a Fish Bowl?

It's important to change fish tank water to help prevent harmful levels of waste chemicals building up, but changing the water more than once a week can do more harm than good. When you do change the water, you need to use aged water. Fresh tap water must be aged to remove chlorine, which is harmful to fish, and doesn't contain the helpful microorganisms that fish need to thrive.

  1. Changing Water

    • Replacing a portion of fish bowl water with clean, aged tap water every one or two weeks helps maintain a healthy environment for fish. Before adding tap water to a fish bowl, let it stand for two or three days beside the tank so the chlorine can evaporate and the water can reach room temperature. Remove 20 to 30 percent of the water in the bowl to avoid changing the chemical composition of the water too much, and to retain a large population of beneficial bacteria. Discard the old, then slowly pour in the clean water. Although water changes are necessary, adding new water to a tank very frequently doesn't provide the stable environment fish require.

    Fish Bowls

    • An aquarium tank provides a healthier environment than a fish bowl and requires a water change only once every three or four weeks. Fish waste contains ammonia, which harms fish if levels get too high. Aquarium tanks hold more water than fish bowls, so ammonia is more diluted and it takes longer for levels to become harmful. A 20-gallon aquarium is suitable for beginners, according to the American Society for the Prevention of Cruelty to Animals.

    Maintaining Water Quality

    • Feeding the correct amount of fish food, installing a filter and cleaning the tank are measure you'll want to take seriously to help keep fish water clean. Feed fish only as much as they can eat within two minutes, and remove any uneaten food, or it will rot and raise ammonia levels. Some fish, such as goldfish, don't have true stomachs and simply excrete whatever excess food they eat. Filters remove waste but require regular cleaning and can become blocked. Check and clean the filter every month. Give the tank a quick clean whenever you change the water. Scrape off any algae growing on the tank walls, remove and clean fish toys and ornaments, and siphon waste from the tank bottom.

    Fish Care

    • Check water quality regularly and observe fish behavior and appearance closely to help avoid diseases and ill health. Pet supply stores sell kits for checking water quality. Use a kit once a month or whenever you have concerns. Fish symptoms that show harmful ammonia levels include red gills and streaks on fins, gasping at the water surface, underactive swimming and black patches on skin, especially along fin edges. These are areas of chemically burned skin that is in a healing state. Affected fish may lie on the bottom of the tank, float on their sides and lose their appetites. Ammonia poisoning is most common in new tanks.