Care guide

Caring for saltwater fish and invertebrates

A saltwater tank is a small ocean you look after every day: stable salinity, temperature and water quality matter more than anything. Cycle the tank, add animals slowly, and quarantine new fish.

Cycle and be patient

A new tank needs four to eight weeks to cycle before animals go in; test until ammonia and nitrite stay at zero. Add a few animals at a time so the bacteria can keep up.

Stable water

Keep salinity around 1.024 to 1.026 SG with a calibrated refractometer, and top off evaporation with fresh RODI water, not salt water. Keep the temperature steady with a heater and controller.

Test regularly and change part of the water often. Invertebrates and corals are especially sensitive to swings.

Quarantine

Quarantine new fish in a separate tank for several weeks to catch diseases like marine ich and velvet before they reach your display tank. Ask sellers how they quarantine.

Choose aquacultured where you can

Aquacultured animals are bred in captivity, already eat prepared foods, and take nothing from wild reefs. Each species' page says where most of them come from; ask the seller about theirs.

Compatibility

Check that new animals suit your tank: some fish nip corals or eat shrimp, and some are territorial. Each species' page lists its temperament and whether it's reef safe.