That is a good idea. I did not think of that. I have already plumbed everything, but it would not be too hard to do that. I will look into it.

My biggest problem seems to be the overflow slowing down. The water level in my tank will stay constant for a few days and then the CPR just decides to slow down. Does the height (or depth) of the powerhead attached to the pre-filter make any difference?

I might have an air leak somewhere in the pre-filter. It was slightly damaged during shipping and I fixed it, but I did not look at the top. I will check it out for air leaks.