Jaws,
I have a 180 that has one hole drilled in the bottom pane of each of the front corners about 6" from the edge of the glass I had the flow runing straight up from a dart on a CL didnt notice a whole lots of back to front movement but I do also have two returns from the CL exausting toward the front of the tank disrupting that flow. I did however just add some OM omniflow jets
http://www.oceansmotions.com/store/p...b83d4d148f926e and directed the flow toward the back corner on each side now fish are using it as a treadmill
Quinster are you using two 2" intakes for the CL on a dart IMHO you would only need one 2" (Factory recomended to take 2" inlet) or even a 1 1/2". Might save you the cost of an extra hole and weakening the tank.
PS I have a 1 1/2" intake on a dart and the pumps are shipped with a 2"-->1 1/2" adaptor