[ozyreefa]

I dont know where people are going wrong with this, if you have a bulkhead over flow, put something over it to partially block it, you will notice the water level in the sump drops a little and the level of water in the tank raises a little. Thats it.The only way it would create more head pressure is if you needed to make the return pipe taller, which you will not. I suppose alot has to do with where your return pipe enters the tank, but for the majority of us who have the return just below the surface of the water, the increase in head pressure would be fractional, particularly with returns that loop over the top of the tank.