FAQ: Health for fish

Most fish diseases do not pass to people, but aquarium water can contain bacteria that in rare cases cause skin infections through small cuts. Wear gloves if you have cuts on your hands and wash your hands afterwards. If a wound will not heal, see a doctor.

Always wash your hands after tank maintenance or feeding and teach children to do the same. Keep medications, water treatments and tests out of children's reach, never start a siphon by mouth, and do not pour tank water into the kitchen sink where food is prepared.

It depends on the medication: some require a partial change between doses, others that the water not be changed for a set time. Follow the label or the vet's instructions, and ask what to do if water parameters worsen.

Some conditioners contain additives that help maintain the fish's protective slime layer, for example after transport, netting or a water change. This can reduce stress, but such products are not medications and do not cure disease.

No. Water conditioner prepares tap water by neutralising chlorine and other substances, so it helps prevent problems, but it does not cure diseases. If fish are sick, test the water and consult a specialist.

Some conditioners temporarily bind ammonia into a less harmful form, but they do not remove it, and tests may still show it. It is only temporary help: deal with the cause through water changes, moderate feeding and a working filter.

Conditioner is usually needed when changing water during treatment, but some medications can interact with certain additives. Read the medication label and, if in doubt, ask a vet.

Leaves and wood release tannins that slightly acidify and tint the water, creating more natural conditions for some soft-water species and reducing stress. But they are not a medicine and do not cure disease.

Useful items are water tests, conditioner, a spare heater, an air pump with an air stone, a seeded filter sponge, a separate net and a box for a temporary tank. Buy medications only when you know what they are for, after consulting a specialist.

Wrong or fluctuating temperature is a common cause of fish stress and disease, and a faulty heater can overheat or chill the water within hours. A thermometer lets you notice in time, so glance at it every day.

Shoot close up through clean glass, without flash and in good light, from several angles so the affected areas show. A short video helps show how the fish swims and breathes. Include the water test results too.

Heaters and air pumps sometimes fail unexpectedly, often at weekends or at night. With spares you can replace a failed device straight away and avoid a temperature drop or oxygen shortage, which quickly harm fish.

Call first: some vets consult from photos first or visit in person. If you do take it, carry the fish in a bag or sealed container of tank water inside a cool box so the water does not chill, and keep the trip as short as possible.

Water parameters often explain why fish are unwell, so the vet may want to test them. Take the sample in a clean, unused lidded container just before you leave and do not add any products to it.

Yes. At night many fish rest, swim slowly, stay near the bottom or among plants and go pale. Nocturnal species, such as many catfish, become more active instead. This is normal if the fish behave as usual again in the morning.

Yes, in many species fish colour up more brightly before or during spawning, some develop contrasting spots or bands, and females may fill out. It is natural if the fish otherwise behaves normally and eats.

Most often with new fish, plants, snails, live food from the wild or shop water. That is why new fish are worth quarantining, plants should be rinsed and checked, and shop water should not go into the tank.

Many bacteria and other microorganisms live in an aquarium all the time and do not harm healthy fish. They become dangerous when fish are weakened by stress, poor water or injuries. Good conditions are therefore the main protection.

That way you quickly notice if a fish is missing: a dead fish left unnoticed among plants or decorations rots and fouls the water. Daily watching at feeding time also helps catch the first signs of illness early.

The difference is mainly the form and how they are used: liquids are added to the water, tablets or powders are dissolved, and some are meant for mixing into food. Which form is suitable depends on the medication and the disease, so follow the label and the vet's directions.