Quarantining new fish in a separate tank for two to four weeks before introducing them to your display aquarium is one of the most effective ways to protect your existing livestock from disease. Many illnesses have incubation periods during which fish appear healthy but are already carrying parasites, bacteria, or viruses.

Set up a simple quarantine tank using a 10 to 20 gallon aquarium with a heater, a sponge filter seeded with beneficial bacteria from your main tank, and a basic hiding spot like a PVC pipe or plastic plant. Bare-bottom tanks are easier to keep clean and medicate. Fill the tank with dechlorinated water matched to the temperature and pH of your display tank.

When you bring new fish home, float the sealed bag in the quarantine tank for 15 to 20 minutes to equalize temperature, then slowly mix small amounts of quarantine tank water into the bag over another 15 minutes before netting the fish into the tank. Discard the store water rather than pouring it in.

During the quarantine period, observe the fish daily for signs of disease: white spots, clamped fins, rapid breathing, loss of appetite, unusual swimming patterns, or visible lesions. Test water parameters regularly and perform partial water changes as needed.

Some hobbyists run a prophylactic treatment course during quarantine using a broad-spectrum anti-parasitic medication, but this is optional and should be researched for your specific species. After two to four weeks with no signs of illness, you can acclimate the fish to your display tank.

Always wash your hands and avoid sharing nets or siphons between quarantine and display tanks without disinfecting them first.