Is It Ich? OR SOMETHING ELSE? When we first started producing butterfly koi back in the 80's, we got a call from a customer about Ich (whitespot) on butterfly koi he had just received. I examined the ones we had left and saw no evidence of Ich. I told him to to treat them and let me know how they responded. A month later he called back and said the fish were doing great, but some still had Ich on their tail fins. So I looked at ours again. And sure enough there were Ich looking spots on a few of the tails. I did a microscopic exam and find that those spots were not Ich, but were tiny fractures in the rays of the tail fin that had calcified as they healed. Ich Imposter Without a microscope, how can you tell the difference? Typically, you'll see the injuries confined to just the tail fins. If the fish do indeed have Ich, you should see the spots on the other fins as well. In many cases, you'll find that Ich will cause fish to "flash" or lie on the bottom, motionless. The broken fin rays will not cause any behavioral changes.