i have one...he's great. No problems at all in a 55 or 70, he swims in and out of the rockwork all day and when its feeding time he's the first one to the turkey baster!!! I'm selling mine to a member of the this forum as we speak....gotta make room for the emperor
Potters are dwarf angels. A 30 gallon is a pretty small tank. If you decide to do a potter's angel, I would make that the biggest fish.
They are a difficult fish to keep and should only be attempted if you have a very established aquarium of about a year.