Well, after a week or so of tweaking everything, I finally have this "mini refugium" setup working. Here's a video and a picture:
YouTube - ‪Current 150G Fish Tank Setup‬‎
Most of my issues came from the pipes making a gurgling noise. The solution is to make sure that the pipes aren't clogged at all, and it helped to have those notches in the top so that it was less likely to make an air-tight seal or have air bubbles when the flow decreased for whatever reason.