How to Acclimatise and Release Fish

The first hour in a new pond is the most important hour of your fish's life with you. A slow, gentle introduction lets them adjust to a new water temperature and chemistry without shock, and it sets them up to settle quickly and thrive.

The good news is it's simple. All it takes is a little preparation, about half an hour of patience on delivery day, and a few days of keeping an eye on things. Here's exactly what to do.

Before your fish arrive

A little preparation in the days before delivery makes release day stress-free for you and your fish.

• Check your water. If you've recently filled or topped up the pond with tap water, treat it with a dechlorinator and give it time to settle. A simple test kit will tell you whether things like ammonia and nitrite are where they should be.
• Get the oxygen flowing. Make sure pumps, filters, fountains or air stones are running well. New fish use a lot of oxygen while they settle in.
• Make sure there's somewhere to hide. Plants, deeper areas and a bit of cover help nervous fish feel safe in their first few days.
• Plan your delivery date. Our fish arrive before midday, so choose a date when someone will be home to receive them. Fish shouldn't be left sitting in their boxes for longer than they need to be.
• Fishery owners, have your permit ready. If your water needs a stocking permit, we'll need the full permit before your order goes out, not just the permit number.

Step by step: acclimatising and releasing

1. Keep the box in the shade. As soon as your delivery arrives, take the box to the pondside and keep it out of direct sunlight. Leave the lid on until you're ready to start.
2. Open up and check on your fish. Take the lid off and have a look. If you have a thermometer, compare the water temperature in the box with your pond.
3. Add pond water slowly. Every few minutes, add a small jug of pond water to the box. Keep going for around 20 to 30 minutes, until the water in the box feels the same temperature as the pond. The bigger the difference, the longer you should take. If the box starts to get too full, carefully pour a little water away.
4. Move your fish gently. Using a soft, knotless net or wet hands, lift each fish into the pond and let it swim away in its own time. Never drop or throw fish in.
5. Give them peace and quiet. Your fish may dart for cover or sit near the bottom for a while. That's completely normal. Leave them be and let them explore when they're ready.

Stocking a lake or fishery? The same principles apply. Release fish in small groups at the water's edge rather than all in one spot, and choose a calm, shaded area with good depth close by.

The first few days

Hold off on feeding. Don't feed your new fish on release day. Wait 24 to 48 hours, then start with small amounts. Little and often is best, and only give them what they'll finish in a few minutes. Uneaten food breaks down and affects water quality.

Keep the oxygen up. Leave pumps and aeration running, especially in warm weather when water holds less oxygen.

Don't worry if they hide. Tench in particular are famously shy, and many fish keep a low profile for the first week or so. As they settle, you'll see more of them.

Signs something isn't right. Keep an eye out for fish gasping at the surface, lying on their side, or swimming with their fins clamped tight to their body. Gasping usually means low oxygen, so boost aeration straight away. If you're worried about anything, get in touch and we'll help.

Need a hand?

Every fish we send is collected from the farm the day before delivery and travels with our specialist live fish courier, so they arrive in the best possible condition. A gentle release is the last step in getting them safely home.

If you have any questions before or after your delivery, email us at customerservice@coarsefishdirect.co.uk and we'll be happy to help.