Regularly cleaning a fish tank helps keep fish healthy. According to the Colorado State University Veterinary Teaching Hospital, uneaten fish food, fish feces and plant debris produce ammonia, which is toxic to fish. Aquarium bacteria convert ammonia to another toxic chemical called nitrite. Reduce both harmful chemicals by removing waste and debris, replacing a portion of the fish tank water regularly, and deep-cleaning on a timely schedule.
Removing Waste and Debris
Use a small net to remove uneaten fish food, fish feces and plant debris that collect on the gravel at the bottom of a fish tank. The Humane Society of the United States says you should scoop out waste and debris every other day.
If your fish regularly leave some food uneaten, you're feeding them too much. Reduce the amount you give until the fish eat it all within two minutes. The ASPCA advises feeding fish several small meals spread out over the day.
Algae grow on fish tank walls, making them unsightly. Scrape algae off the walls every one to two weeks -- before you change the fish tank water. Use a special algae scraper, which won't damage the glass.
Fish like to nibble algae. Leave a little to grow in a hidden corner.
Cleaning Gravel and Changing Water
The best time for cleaning gravel in a fish tank is just before you change the water. The Humane Society says you must change a portion of fish tank water every one to two weeks, or when the water looks cloudy. It's a multiple-step process:
- Prepare replacement water by standing fresh, clean water for two to three days so the chlorine within the water evaporates. Prepare a volume that's a little more than 20 percent of your tank's capacity. You can accelerate the process by adding dechlorinating tablets or liquid to the water. Regardless of how you remove the chlorine, make sure the replacement water is the same temperature as the water in the fish tank.
- Carefully remove about 20 percent of the fish tank water, using a special filtered siphon for aquariums, or a jug or other container.
- Clean the gravel with a gravel vacuum. Gently push the vacuum into the gravel and lift so the gravel falls below but the waste and debris get sucked up.
- Pour the replacement water into the tank slowly.
If your fish seem unhealthy or you're worried about water quality, test your fish tank water with a kit from an aquarium store.
Filters help keep fish tank water clean, but they also need cleaning themselves. Some filters contain disposable cartridges; other filters contain permanent fittings, such as sponges, rotating wheels or ceramic noodles.
Fish Channel.com advises replacing one disposable cartridge at a time with double-cartridge filters. Replace activated carbon cartridges and rinse filter pad cartridges. Two weeks later, replace the filter pad. In another two weeks, replace the carbon cartridge and rinse the filter pad again.
The ASPCA says that you should clean filters every month. Rinse permanent filter fittings under clean, cool, running water, as necessary.
Don't [sterilize filters or let them dry out](http://www.fishchannel.com/fish-health/healthy-aquariums/dont-destroy-helpful-bacteria.aspx), or you might harm beneficial bacteria.
Fish tank plants need pruning when they grow too large. You can prune plants with clean scissors or pruning shears. Snip off the leaves and take them out of the water so they don't decay and create ammonia.