I apologize that no one has responded to your question sooner. Different experts come online at various times. I just logged on and saw your question. My name is ***** ***** I’m a biologist with a special interest in fish. I'm sorry to hear of Mikie's problem.
There are two likely explanations for this white spot. One is that the fish bumped his eye on something. A minor injury can cause a white spot to appear. It can be temporary or permanent. There are also fungal infections that begin with a white spot in the eye. The first thing I would try is aquarium salt. If there is an injury, it can soothe it and also helps fish cope with stress. Use one teaspoon per gallon of water.
A mild fungal infection may also respond to salt, but if such an infection is even slightly advanced, you'll want to treat more aggressively. There are many antifungal medications sold in pet stores. Pimafix is one of the more mild ones. If you want to use something stronger, it would be best to put Mikie in a hospital tank so you're other fish isn't subjected to medication it doesn't need.
A third option is to consult an aquatic vet. The vet can observe the eye first hand, and can also apply treatment directly to it if need be. If you want to do that, this link will take you to a directory of fish vets.
If you have more questions, just let me know. I hope that whichever option you choose, Mikie will be fine.
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