Oh and my return column with the rock may not be ready for the install date of 7-5 I realized I should have done something a little different with the rock so it's do over time. I'd rather be safe than sorry later. What I should have done was to use 1 inch or larger pvc pipe down the center and removed it after it hardened. By using the 3/4" (the actual return size and pipe) it would add weight and pressure to the bulk head. This is a major no-no. If I use a larger size pipe, remove, then replace it with the 3/4" there is no weight on the pipe or bulk heads and even has wiggle room. No loss though, except for time. I'll use this rock in the tank regardless