When Your Fish Arrive (acclimatisation guide)

When your fish get home

The way you introduce new fish to your tank matters just as much as the journey home. Choose the column below that matches how you bought your fish.

Bought in-store

  1. Get them home promptly. Fish travel best in a dark, insulated bag — avoid leaving them in a hot car, direct sunlight, or in transit for longer than necessary. If your journey is more than 30–40 minutes, ask us for an insulated bag or box before you leave.
  2. Check the bag before you start. If a fish looks distressed, or the water is unusually cloudy, contact us straight away.
  3. Follow the acclimatisation steps below.

If a fish is lost after purchase: see our Refund & Exchange Policy for our in-store process, including timescales and the water test we'll need.

Bought online

Your fish travelled overnight with our livestock courier. See How Live Fish Delivery Works for how delivery is scheduled, and unbox as soon as your delivery arrives — don't leave the box unopened.

Check the bags. Cloudy water, or a fish that looks distressed or upside-down? Photograph the bag now, in good light, and email info@birchwoodaquaticcentre.co.uk with your order number within 4 hours.

Once checked, follow the acclimatisation steps below.

If a fish is lost after delivery: see our Live Arrival Guarantee for cover on arrival and the first seven days, and how to claim.

Acclimatising your fish

  1. Float the sealed bag. Float the unopened bag in your aquarium for 15–20 minutes so the temperature equalises.
  2. Add tank water gradually. Open the bag and add a cupful of your tank water every 5 minutes, three or four times. This lets the fish adjust to your water chemistry gently.
  3. Net the fish into the tank. Lift the fish out with a soft net and release it into the aquarium. Discard the bag water — never pour it into your tank.
  4. Lights low, no food. Keep the lighting dim for the rest of the day and skip feeding until tomorrow. New arrivals settle faster in a calm, quiet tank.

New fish may hide or look pale for a day or two — that's normal, and colour and confidence usually return within a few days in a settled tank. If a fish still looks unwell or isn't eating after a week, get in touch and we're happy to advise.

Marine fish, corals and invertebrates are more sensitive to sudden changes in water chemistry and typically need slower drip acclimatisation than the steps above. These steps apply to freshwater and pond livestock.