Like most pets, fish can occasionally get sick. There are many texts which describe what you can do for your dog, cat or budgie if they become ill, but what do you do for your sick fish? Here are some simple steps to follow when you notice something is not quite right with your fishy friend:

Check the tank and accessories

Make sure the air stones are working properly; check for kinks in the air lines; check the water flow around the tank to see whether the filter inlets are functional, and whether the filters are moving water around; check the tank temperature to see whether it is too hot or too cold (remember to turn the heater off at the wall and un-plug it first); check the water level in the tank to see it hasn't dropped below levels that allow proper filter operation. Good aeration is essential for infirmed fish.

Check the water quality parameters

Each fish has a level of water quality within which it likes to live. Make some notes of the levels which your fish should like to live in, and have them handy for when problems arise so you can compare. Measure pH, total ammonia levels, nitrite, nitrate, temperature, hardness and alkalinity. This can be done by purchasing simple colour comparison test kits and keep them on hand as an insurance against disaster. Just follow the simple instructions and make a note of the levels that you have in the tank for comparison against the levels you should have in the tank.

Change 30 - 40% of the water in the tank

Change 30 - 40% of the water in the tank with clean aged water. This water needs to be de-chlorinated and have the water parameters that your fish require. If you have found high ammonia, nitrite or nitrate levels with your tests, this water change will help dilute the levels down to less toxic levels.

Add a balanced salt formulation

Adding a balanced salt formulation (or fresh water if the tank is marine) helps balance the salt/water content present, which reduces the stress on the fish. It’s a bit like having fish on a drip. Levels of salt from 2 - 5 grams per litre will be well tolerated by most fish. There are some fish that don't tolerate salt at all (e.g. some of the catfish), so make a note when you buy your fish as to their tolerance to salt. 24 - 48 hours in a salt bath will help a lot, whilst you investigate a cause of the health problems. Fish disease can be diagnosed as for any other domestic animal, so seek out a qualified veterinarian for this advice.

Remove any bodies

If there has been a serious mortality rate in your fish tank make sure that you remove any bodies.

Compile a complete history

Compile a complete history of the fish tank for the last two weeks prior to the problem arising. Every little detail can help. Include introductions, water exchange history, when, with what water, what treatments, new fish, new plants etc. Even if the details seem silly to you, make a note, as it may be the little details that help the diagnostician come up with an answer. Any fish that have died need to be collected fresh if they are going to be useful for diagnostics. Wrap the animal in a plastic bag and place it in the fridge. If it is older than two days, it will be of little use and can be disposed of or buried.

Most of all don't panic, and avoid using the cocktail, 'shot-gun' treatments that usually cause more stress on your fish than they alleviate.