I've got a 110 gallon main tank with a 30 gallon sump. Sump has a few pieces of LR and Caulerpa and Chaeto in it. Main tank has about 200 lbs of LR. I've read conflicting opinions on how much return flow there should be. I've read the higher the flow the better. I've read the slower the flow the better. I've also read the rule of thumb is 3-5x turnover. Is this 3-5x the total water volume of the entire system (140 gallons in this case), or is it just the main tank volume? Do you take into account water displacement from the LR? For example, my system probably only has about 90-100 total gallons of water in it if you take into account the rock.