Why do the new fish I buy for my aquarium die while my others are “ok”?

Firstly, do ensure that the water conditions in your aquarium are safe and within acceptable levels for the new fish you’re adding. Test your water parameters and perform any maintenance needed to ensure that they’re all optimal. Remember that established fish may have adapted to conditions over time that can fatally stress newly-introduced individuals - even of the same species.

Next, consider your method of acclimatising new fish. The lights of the tank should be switched off and the bag containing the new fish should be floated for at least 10-15mins to allow the temperature to balance. Next, cut open the top of the bag and roll down a collar to allow the bag to float on the water’s surface. In this position, you can safely "dip" the bag to allow small amounts of tank water to mix in with the bagged transport water. By repeating this procedure every 10 minutes, you can ensure that the fish are very gently acclimatised to your tank’s water.

When the bag is full or nearly full, you can carefully tip the contents out and allow the fish to swim directly into the tank, or alternatively, remove the bag and gently pour the water and the fish through a net into a small bucket. The fish will catch in the net, while the mixed transport water ends up in the bucket. You can then safely add the fish to the tank.

You might need to consider a few other potential pitfalls. Remember that from the moment the fish are in the bag and being transported, they are under stress. Are they being carefully transported home? Is the bag being unduly shaken? Are you travelling for a long time after purchasing the fish? Have you made every effort to avoid exposing them to temperature changes or bright light on their journey? Often a bag such as Maidenhead Aquatics Thermal Fish Transportation Bag will help give your new pets the best start to their journey home.

Also, you might need to consider the health of the fish you are buying. Some species are hardier than others and adding delicate fish to an unsuitable tank can be a disaster. Ask at your local Maidenhead for advice on which fish will live happily together. We take great care in sourcing all our fish and providing them with the best conditions possible in the hope that they will do well in your aquarium. With your help they hope to live a long and happy life in good conditions.