They are built wide and front to back deep. And they are shallower than a regular tank. So it has a lot of surface area and is not real deep, compared to a regular tank. A 30 breeder is only 11 inches tall but 36 long by 18 or so deep(front to back). A 40 is the same footprint but deeper, I think 18 tall. Fish farms around here use the 30 breeders a lot, and drill the bottom and use an overflow.