I just purchased an aquarium to use as a frag tank. I am a little confused because the tank has a hole drilled in the corner but with no overflow box and no bulkhead fitting, it is just a tank only. I am confused as to one is a overflow and what about a return???? So how would I plumb this to my display tank? Do I even need a overflow box or do I need to drill another hole? If anyone can help me, it would be greatly apprciated. Thanks in advance