Q The fish in my pond keep dying. How can I stop this?

A There are many reasons why fish die and you will need to do a bit of investigation to pinpoint the problem. You can buy water-test kits to help diagnose water-quality problems, such as the wrong pH, or high levels of ammonia, nitrates or chlorine.

Caption: Herons can target garden ponds

Other problems can arise from gardening activities. Watch out for chemical poisoning; lawn fertilisers and weedkillers can easily wash into garden ponds. You also need to be wary when you use pesticides on nearby plants, as these can wash into the water. Other problems are more common at certain times of the year. In spring, the majority of pond water is cold, but on hot days the top few centimetres and the shallows can heat up considerably. Coupled with this, plant growth can be slow, leading to reduced oxygen levels.

Fish can also be affected by disease, so get to know your fish and keep an eye out for parasites, bacteria or fungal problems. You should try to protect them from predators (cats, frogs, herons, kingfishers etc), and physical trauma from being sucked into pumps or filters. Also remember that stress can kill, so avoid overcrowding or repeatedly netting or moving the fish.