Fish Tank Care: Cycling, Cleaning and Feeding

Fish tank care comes down to three jobs: cycle a new tank for 4 to 6 weeks before fish go in, change part of the water and vacuum the gravel on a regular schedule, and feed a small amount once a day. Most problems in a home aquarium trace back to skipping one of the three.

The chapters in this section walk through each job with the numbers vets, welfare groups and makers give.

Cycle a new tank before fish

Cycling grows the bacteria that turn toxic ammonia from fish waste into nitrite and then less harmful nitrate. VCA says a new tank needs 4 to 6 weeks before fish go in, and UF/IFAS puts a new biofilter at 6 to 8 weeks. A liquid test kit shows when ammonia and nitrite reach zero. How to cycle a fish tank explains fishless cycling step by step.

Water conditioners, test kits and bacteria starters

Shop water conditioners, test kits and bacteria starters→

Opens eBay in a new tab. Check condition, seller feedback and returns.

• Water conditionersBrowse →
• Liquid test kitsBrowse →
• Bacteria startersBrowse →

Test the water on a schedule

Ammonia and nitrite are the readings that matter most. RSPCA Australia says ammonia is toxic to fish from 0.1 ppm, and UF/IFAS says nitrite can be toxic at 0.10 mg/L. Nitrate builds up more slowly and comes out with water changes.

If fish are already in a tank that has not cycled, RSPCA Australia says to test ammonia and nitrite every 2 to 3 days for the first six weeks and to change 10 to 25 percent of the water every 2 to 3 days. Once the tank is stable, a test before each water change shows whether the routine is keeping up.

Clean the tank without losing the cycle

Clean a tank by changing part of the water with a gravel vacuum, never by emptying it. The sources differ on how often:

Treat new water with conditioner and match its temperature. Rinse filter media in old tank water, not tap water, so the bacteria survive. The Marina kit manual says never to use soap or detergent on anything in the tank. How to clean a fish tank covers algae and gravel vacuums too.

Feed less than you think

Feed a small amount once a day: RSPCA Australia says only what the fish eat in under two minutes. Overfeeding fouls the water, so a pinch too little is safer than a pinch too much. Bettas take betta pellets or flakes, goldfish a goldfish food, and University of Illinois vets say freeze-dried treats are fine in moderation. The fish food guide covers each type and vacation feeders.

Care chapters at a glance

The filter and heater that keep the water stable are in the equipment section. The same water rules apply outdoors in garden ponds.