I was wondering what the minimum permanent tank requirement would be for 2 Oranda Goldfish? I don't know if this matters but I was hoping for 1 RedCap and 1 Black/Blue. I'm confused because a lot of websites are saying to go for 30 Gallon Per fish and others say to follow the standard fancy goldfish rule of 20 for the first and add 10 per additional fish, I was thinking about doing 30 Gallon but I'm afraid that it won't be enough room since goldfish get huge. And would getting two smaller filters be better than 1 bigger one? I was looking at HOB filters but I was also considering doing canister.