It could be a parasitic infection causing over production of the slime coat or a bacterial infection I think the best course of treatment would be to do a course of paracleanse to treat the tank and a do a course of maracyn in food using this food recipe that will cover most bases I would repeat the paracleanse every two weeks for a total of 3 full course of paracleanse if you can't get them to eat you could do a course of paracleanse then follow up with a course of maracyn then repeat the paracleanse on week3 and week5@Scottdd2002