okay, in answer to your original question, the black moor most likely has fungus and there are medications at Wal-Mart and the pet store made for that purpose. But here's the deal, though. Some websites say you can get by with less but what I have read the most is that goldfish need 20-30 gallons for the first fish and 10-15 gallons for each additional fish. Some people claim that that is not even enough room. Shocking, isn't it? I don't understand why they even sell goldfish bowls seeing how they're completely innappropriate. So basically, even a ten gallon will not safely house your goldfish. When goldfish "grow to the size of the tank" such as a 10 gallon they are stunted and will always be prone to illness. They will most likely not live very long either. Also, I just had to get rid of my pleco because he outgrew my 55 gallon tank. They do eat algae but they poop so much that all they do is make your tank nasty. They can get over a foot long so as you can see, he's not appropriate for your 5 or 10g either. Also, the reason why you are not supposed to mix goldfish with bettas or plecos is because the food and temperature requirements are different for goldfish. They are coldwater fish and the others are tropical fish. Oh, also bacteria enhancers, to my knowledge, the only one that actually works is biospira. Unfortunately, you are somewhat limited on what you can put in a 5 gallon tank however I'm sure plenty of people would love to give you some stocking suggestions. My advice is to get rid of all those fish, take them to the pet store (unless you want to keep the betta), cycle your tank and start over with some different fish. That may not be what you want to hear and I hope you're not too disappointed. Welcome to aquaria central and I hope we've been some help.
