Koi Health - Koi Clubs USA
Regular observation of your fish will allow problems to be detected early. Be familiar with your fish's normal shape, size and color as well as swimming habits.
A change in these factors may signal a problem. The problem must be identified in order to know the steps to take for treatment. Every pond owner with fish, at some time or another, will probably have to medicate their pond.
Though Koi and Goldfish are extremely hardy, it is very important to keep a watch on their environment to keep them at their healthiest.
Attention should be paid to the quality of water and balance of the pond (i.e. pH levels etc.). However, if problems do occur, the first step is to remove the individual fish or decide whether to treat the entire pond.
It is sometimes difficult to be aware of a problem with a fish until its too late. Be aware of your fish's behavior patterns so changes can be detected early. A change in your fish's behavior is usually the first sign that that your fish are stressed or ill.
It is important that you know your pond's volume. All treatments are based on the number of gallons in the pond. The wrong dosage could result in killing your fish.