I was wondering if it is necessary to have a break in your waters surface? I can create a break using my return but was thinking the overflow would be more effective if the return lines were pointed down giving more flow deeper in the tank. I guess the main concern would be oxygen in the water, but my water drops down about 6" in the overflow, and I use a large skimmer. Would this be sufficient or is having a break on the surface better? What are pros and cons of both?