There should be two parts to the overflow box. On sits on the inside of the tank with the notches in it, the other box is on the outside. Thjis outside box is the one you connect the tube to.
The water comes in to a certain point where the edges of the teeth are and then the plastic J tube looking thing brings the water from the tank box into the back box and down it goes.
hope that helped
180g Reef - 60g Rimless Reef -90G FOWLR- 125g Malawi Cichlids- 40b REEF- 34g Fresh Planted-working on- 20L FOWLR- working on
I have a mix of many different saltwater fish amongst my tanks, but I love my Tangs most of all.