Hi, I have a 10 gallon freshwater aquarium. I've been maintaining it pretty well for over 15 years, w. only occasional hiccups. Two goldfish (one is 17 years old, and the other is about 8 years old). Plus an algae-eater. Got a dramatic problem (big red bumps and general swelling by gills on one side) with the largest & youngest one--think it is bacterial so am treating it with tetracycline. Just started tonight. Been reading on Internet, not sure what is best. I am not sure how to use chats & advice forums on this site.