dankoos
Member
I understand how an overflow that hangs onto the aquarium works, however, I don't quite understand the pre-drilled version. The holes are drilled on the bottom or back of the tank? Does the water flow over the internal overflow and then down through the holes? How do you "seal" the holes to prevent leaks? I take it the sump has to be able to hold all the built in overflow can handle? Just trying to get a grip on the concept. Should I go w/ pre-drilled or not? Thinking of a 75g tank. Thanks