Care guide

Caring for reef corals

Corals do best in a stable, established saltwater tank. Match the light and flow the seller kept the frag in, acclimate it slowly, and keep the water steady rather than chasing perfect numbers.

A stable reef tank

Add corals only to a cycled saltwater tank that has been running for a while, with stable temperature (about 25 to 27 °C) and salinity (about 1.025 to 1.026 specific gravity).

Stony corals (LPS and SPS) use calcium, alkalinity and magnesium to grow. Test those regularly and keep them steady; sudden swings do more harm than numbers that are slightly off.

Light and flow

Ask the seller what light and flow the frag grew under. Start it lower in the tank than you expect, out of strong direct flow, and move it up over a few weeks if it looks healthy.

Soft corals and many LPS are forgiving; SPS generally need strong light, strong flow and very stable water.

When it arrives

Float the bag to match temperature, then slowly add tank water over 20 to 30 minutes. Many keepers dip new frags in a coral dip and inspect them for pests before they go in the display tank, or keep them in a separate quarantine tank first.

Give it space: some corals sting their neighbours. Hammer, torch and frogspawn corals send out long sweeper tentacles at night.

Handle with care

Wear gloves when handling corals, and eye protection when cutting or scrubbing them. Some zoanthids and palythoa carry palytoxin, which is dangerous if it reaches the eyes, mouth or a cut. Never boil rock with zoanthids or palythoa on it.

Rules for buying and selling

Stony corals are listed under CITES. Moving them across the Canada–US border needs export and import permits, so most hobby frags are bought and sold within the same country.