How often should you clean a fish tank

The short answer

If you do the upkeep yourself, most freshwater tanks want a small water change and a glass cleaning every one to two weeks and a filter clean about once a month. On a professional schedule, most freshwater tanks are serviced every two to four weeks, because each visit is a full service instead of a quick change. Reef tanks need attention weekly or every two weeks. Fish-only saltwater tanks sit in between. The tank decides, though, not the calendar: a lightly stocked 75 gallon tank and a crowded 20 gallon tank are different jobs even if they hold the same fish.

Freshwater community tanks

Change 15 to 25 percent of the water every one to two weeks, using conditioned water at the same temperature. Vacuum the gravel where waste collects, usually the front and the corners, rather than the whole bed at once. Wipe the glass, check the heater and look at every fish. Once a month, rinse the filter sponge in the water you just took out of the tank, never under the tap. Tap water kills the bacteria the filter depends on.

Planted tanks

Planted tanks want a larger weekly water change, often 30 to 50 percent, because fertilizer builds up and algae is waiting for any imbalance. Trim fast-growing stems every week or two so they do not shade everything below them. Clean the glass before the change so the algae you scrape off leaves with the old water.

Saltwater and reef tanks

A reef does best on a weekly or bi-weekly visit: 10 to 15 percent water change with saltwater mixed and matched to the tank's salinity and temperature, glass cleaned, skimmer cup emptied, filter socks swapped, and alkalinity, calcium, magnesium, nitrate and phosphate tested and written down. Small, steady changes beat big, occasional ones. A reef that gets a 40 percent change once a month swings far more than one that gets a little every week.

Fish-only saltwater tanks can often go every two weeks, with the same care on the water going in.

Signs it needs attention sooner

Cloudy water, a film on the surface, algae coming back days after a cleaning, fish breathing hard at the top, a filter that sounds different, or a smell. Any of those means something has drifted, and a water test will usually say what. In South Florida summer, add a heater or chiller check: tanks near a window or in a warm room can run hotter than their owners realize.

When to hand it off

If the schedule keeps slipping, the tank is telling you the honest answer. That is most of what a regular service visit fixes. Jason sets the frequency by looking at the tank and the water numbers, and if your tank needs fewer visits than you expected, he will say so.