You have definitely introduce a fungus into your tank called "eye cloud". It is common when you have bad water conditions such as temperature, oxygen, ph. ammonia. It has been successfully treated through water changes and treatment with Melafix and Pimafix. You can ask your local LFS for advise on other treatments. Also, purchase some aquarium salt and add 1 tablespoon for every 5 U.S. gallons after your water changes. So if you do a 10 gallon water change add 2 tablespoon of salt to your tank. I hope that this helps.