Koi treatment

Koi treatment is a tricky business. It's easy to misdiagnose a disease, or to miscalculate the amount of medicine needed. If you need to treat koi at home, I recommend you do plenty of research. But bear in mind also that koi hardly ever die of old age – almost always of some kind of disease. If you lose koi to illness, the only consolation is that every koi keep has had the same experience.

That said, here's a quick overview to get you started.

There are two main ways you can do your own koi treatment: you can treat an individual koi in a small bath beside the pond, or you can treat the entire pond at once by adding medicine to the pond.

Try to prepare everything you need for the treatment before you remove the koi from the pond, so as not to cause unnecessary stress.

Individual koi treatment

When you need to treat an individual koi, this will usually involve taking him out of the water and putting him in a small bath at the side of the pond for a short period of time. The bath will be made of water from the pond, plus a medicine.

It's a good idea to get a specialist koi net to catch the sick koi – standard fish nets can bend koi too much. Handle the koi gently – koi have a protective mucus layer to ward off infection, and you will damage this any time you touch them with anything dry, so touch them as little as possible, and always wet your hands first.

The bath can be done in an ordinary plastic bowl. You need to measure both the water and the medicines very carefully to make sure the proportions are right, also to be careful with timings so that your koi aren't exposed to the treatment for too long.

If you need to remove the koi from the bath – for example to remove parasites – place him on a thoroughly wetted cloth. You can also cover his head with a wet cloth, which will help keep him calm. If you need to work on him in this way for a long time, remember to put him back in the bath every so often so he can calm down and breathe.

Sometimes you'll want to put the koi into a recovery tank afterwards for several days – this is a larger tank filled with pond water to which salt is added – 25g per five litres of water. It's good for treating lots of koi illnesses – bacterial diseases, parasitic problems, and fungal infections. Make sure the tank is in a quiet, shady place, and provide filtration and aeration.

Treating the whole pond

This involves adding medicine to the pond. You need to know the volume of your pond, so that you can calculate the right amount of chemical to add – too little will be ineffective, too much can be harmful. There are only some chemicals that it's safe to add to the pond – many will damage the bacteria in your biological filter, so always read the instructions carefully.

For many diseases, you'll want to treat the whole pond even after you've treated those koi that are sick, to prevent the disease recurring.

Other methods of koi treatment

There are some medicines that you can give with food – in particular, antibiotics. More on how to do this further down.

For diseases you can't treat yourself, a vet can often administer injections.

Koi medicines and chemical treatments

Many of these chemicals are irritating to the skin or toxic to both humans and other animals – always wear gloves to handle them. They may also have a shelf-life, so replace them regularly.

Malachite green

This is good for treating fungal infections, and some parasites. It comes in powder form. As the name suggests, it's very, very green! Use the zinc-free kind – it's less toxic – but it is toxic nonetheless to humans as well as fish, so handle with care. Goggles are a good idea, and take care not to breathe in the powder. It's often used with…

Formalin

This is also very toxic, and again, don't breathe it in. It's used with malachite green to treat parasites. It lowers oxygen levels, so when you use it, aerate the water.

Metrifonate

This is an insecticide, used to treat parasites.

Antibiotic – Terramycin

Terrmycin is a good general medicine for treating bacterial diseases. It can be used in a bath, and can also be added to koi food. Take a kilo of pellet-type koi food, and mix it up with 8g of Terramycin. Gradually add 20ml of vegetable oil, and mix thoroughly. Then feed your koi in the usual way, once every other day, for two weeks.

Never use an antibiotic to treat a pond directly – pouring antibiotics into your pond will very effectively destroy your biological filter. If you need to treat the whole pond, always use the food method.

Antiseptics

Mercurochrone is a good antiseptic for applying to infected areas – use a cotton bud. Roccal is a good antiseptic for baths, when the infection is minor. Chloramine T is another good antiseptic for baths, but it's a little tricky to use, though, as the amount needed depends on the pH and softness of the water, as well as the volume.

Treatments for particular diseases

Treatment for bacterial infections

Individual bath: Roccal, then a salt-water recovery tank for six days.
Treating the pond: Chloramine T, repeat two days later, and feed Terramycin pellets.

Treatment for koi fungus

Place the koi on a wet cloth (cover the head). Soak a cotton bud in 0.1% malachite green, and use it to gently remove the fungus. Then with another cotton bud, apply mercurochrome to the area. If the case is bad, place the koi in a bath of malachite green before putting him back n the pond.

Treatment for parasites

Treatment for Protazoan parasites:
Individual bath: formalin and malachite green.
Treating the pond: formalin.

Treatment for Trematode worms – flukes and gill flukes
Individual bath: formalin and malachite green.
Treating the pond: metrifonate, 2-4 times over four weeks.

Treatment for Copepod parasites – anchor worm and fish lice
First carefully look the koi over in a bath and find the parasites. Then place him on a wet cloth (cover his head) and very gently remove them with a pair of tweezers. Pull backwards, and don't be too rough, or you risk leaving the heads under the skin. If the case is mild, you may find that a strong salt bath will loosen the parasites' grip – be careful not to make it too strong, though, or you'll make the koi ill!
Treating the pond: metrifonate, every other week for six weeks – or every week for three weeks in warm weather. Feed Terramycin in pellets.

Treatment for gill lice
Individual bath: formalin and malachite green
Treating the pond: as for anchor worm and fish lice

Treatment for hole disease

As for fungus, then place the koi in a salt-water recovery tank. After returning to the pond, feed Terramycin pellets.

Treatment for cuts and injuries

Place the koi on a wet cloth (cover the head). Apply mercurochrome with a cotton bud and return to the pond. Repeat the next day. If infection sets in, feed with Terramycin pellets.