How to acclimate new fish to an existing tank

Before you buy

Confirm your tank is cycled and has capacity for more fish. Sudden stocking is a common cause of disease and ammonia spikes.

If possible, use a separate quarantine tank for 2–4 weeks before the main display.

Simple bag float + drip method

1. Turn aquarium lights down. Float the sealed bag for 15–20 minutes so temperatures equalise.
2. Open the bag and roll the edge so it floats like a cup. Add a small amount of tank water every few minutes for 30–60 minutes (or use airline tubing as a slow drip).
3. Net the fish into the tank. Discard the bag water — do not pour shop water into your aquarium.
4. Keep lights low and watch for gasping, clamped fins, or hiding over the next day.

Aftercare

Avoid big water changes or new decorations on the same day. Feed lightly for the first 24–48 hours.

If fish look unwell, isolate early and seek advice from an aquatic-experienced vet or knowledgeable local store.