I have a black big eyed goldfish. He is in a 10 gallon tank with a upgraded filter and his tank has to be cleaned once a week or it will turn dark green. HELP
To much light causing algae to grow.
Also don't buy those algae sucker-fish because there are semi-ugly and doesn't go with the beauty of your fish tank. I would recommend getting a cleaning shrimp.
It goes with everything and is really cool if you have kids or to just entertain yourself with it. Also the shrimp can clean your fish from bacteria and other bad stuff.