popeye is an infection of the eye due to irritation or injury. it is not contagious so you need not worry about it spreading to the rest of the communtiy. if left untreated it could result in the loss of the eye. i would seperate so as not to be medicating otherwise healthy fish.
ich is a parasite that when it is freeswimming is not detectable to the naked eye. fish infected with ich will shows signs when the parasite is attached to the host. what is the temp of your tank? ich is usually more predominant in the cooler months since the parasite cannot survive in temps 72 or greater. you will have to treat the whole tank. make sure that any equipment that is shared with other tanks is carefully washed out in hot water or boiled to prevent spreading to your other tanks.
there are meds for both popeye and ich available. with the tank with ich i have raised the tank temp to 74, if the fish can tolerate, and do a large water change of 50%. following with water changes every other day of 10%. if there are no other scaleless fish in this tank, i would also add aquarium salt to it. have used this method to rid a tank of ich before.
have you added any new fish into the tank with ich? if so, this is probably your culprit. all new fish should be quarantined for 3-4 weeks before adding to the community. granted that no signs of disease are present after that time, it can then be added to the community.
sf
