Red spots or sores are the earliest stages of bacterial infection [Ulcer Disease] in the skin of Koi. Sometimes, abrasions sustained in the breeding frenzy can become infected.

This is particularly true if it is apparently been caused by the Spawning which often occurs in our ponds during the late Spring and early Summer months .. the spawn, which may be decaying because it is not fertile has fouled the water, or if the fish are crowded.

In addition, some red spots are very commonly caused by infectious parasites which attack the skin, opening it to infection. Flukes are just one example.

in the case of the later then treat for the parasite once they have been identified.