WK, do you have any threads that detail closed loops?
I looked at Anthony Calfo's posts about CL's and I get the general idea of them but I have yet to find any CL's on a drilled tank rather than going over the top and, for lack of a better word, "sitting" just under the water around the perimeter.
I plan on getting an acrylic tank, I'd like to have a CL but would rather not have all that pvc sitting out in the open if possible.