I just took over our tank. Think it's a 10gal, maybe 15. We have a cheetha patterned goldfish (think it's a goldfish) that has some scales missing and is swimming vertically, sometimes upside down. This began several days ago. We also have some kind of japenese yellow sucker (bottom feeder, reminds me of a tiny catfish) and a halfmoon betta. The betta has one bulging cloudy eye. I did a 70% water change yesterday. Ido not know what the specs are, ammonia, ph or nitrates. What could cause my fish to get sick and what can I do to make them well?