Ok, so I am having trouble with designing the plumbing for my 135... Right now as it stands, I have only 3 holes in the tank... A 1.5" for drain and 2 1" for returns... My question is can i do a closed loop system... I do not want to drill anymore holes... If I cannot do a closed loop can someone explain the best way to plumb this thing... On my 60 I simply drilled a hole in the last compartment and ran pvc from the right side of the tank to the left side, then dropped the pvc into the sump... Should I just do the same thing on the 135...