FAQ: Health for fish

A net over the pond, steep or deeper edges and underwater hiding places such as pipes or dense plants help. Fish attacked by predators are often left with wounds, so watch them to see that the wounds do not become infected.

Shrimp are very sensitive to copper, some medications and products, sudden changes in water parameters and poor water. Acclimating too quickly to new water or large water changes are common causes. Test the water and review any products you used.

Moulting problems are often linked to unsuitable water hardness and mineral content or sudden parameter changes. Stable water suited to the species and moderate changes help shrimp moult successfully. If shrimp keep dying while moulting, ask an experienced keeper.

Snails need calcium for their shells, so in very soft or acidic water shells thin and develop pits or white patches. Moderately hard water and food with enough calcium help.

Marine fish are often more sensitive to water changes and transport, and many are wild-caught, so quarantine is especially important. Many medications also harm corals and invertebrates, so treatment usually needs a separate tank.

Usually not. Many marine fish medications, especially those with copper, harm corals, shrimp and other invertebrates. So fish are usually treated in a separate tank, and the label must be read before using any product.

As water evaporates, salinity rises, and topping up with too much fresh water drops it suddenly. Such swings stress marine fish and invertebrates. Measure salinity regularly and top up evaporated water often in small amounts.

Often, yes. Breeds with round bodies, long veil fins or enlarged eyes swim more slowly, have swim bladder trouble more often, and injure fins and eyes more easily. Clean water, gentle flow and smooth decorations are especially important for them.

Stable water, easy-to-eat food and less competition from faster tank mates matter especially for old fish. They may be slower and paler. Make sure they get food, and do not mistake sudden signs of illness for old age.

Fry need very clean water, so small water changes are done often and uneaten food is removed. Feed fine food of the right size often in small portions, and do not overcrowd the rearing tank.

Yes, spawning exhausts fish, and males often chase and injure females. After spawning fish need peace, good food and clean water, and an exhausted or injured fish is worth separating for a while.

Use separate nets, siphons and buckets for each tank, do not move water from one tank to another and wash your hands between jobs. Service the healthy tank first and leave the quarantine or hospital tank until last.

If the tank needs a full clean, drain it, wash the tank and equipment, disinfect with a product suitable for aquariums as the label directs, rinse very thoroughly and let it dry. Some diseases are resistant, so it is worth asking a vet about disinfection.

A UV steriliser reduces free-floating microorganisms and algae in the water, but does not affect pathogens on the fish or in the substrate. It can be a useful extra measure, but it does not replace quarantine, good water or treatment.

A dead fish quickly starts to rot and raises ammonia, and if it had a contagious disease, other fish eating it may become infected. That is why a dead fish should be spotted and removed as soon as possible.

Remove it with a net straight away, test the water and temperature and look over the other fish. If the water is poor, change part of it. If fish die one after another or show signs of illness, contact a vet.

Some fish rest lying on the bottom, on their side or wedged among plants. Check whether the gills move and gently stir the water nearby: a live fish usually reacts. If in doubt, wait a few minutes and watch.

Wrap the dead fish and put it in general waste, or bury it deep enough and away from water bodies. Do not flush it or put it in natural waters, so pathogens do not spread. If you want to find out the cause of death, contact a vet.

Aquarium fish can spread diseases and parasites to native fish, and some species become invasive and damage nature. Many also die in the wild. If you can no longer keep your fish, offer them to other aquarists or a shop.

Contact a vet, who can assess its condition and, if needed, put the fish to sleep humanely. Do not attempt it by flushing the fish or by other methods that cause prolonged suffering.