When I first set up a 1" PVC overflow on my tank it was incredible noisy (however quite amusing-like having a flatuent uncle in the basement). I chuckled until I found all my fish in the fuge. I put a sponge filter from the intake on a magdrive pump over the opening until I could make a gurgle buster. The noisy uncle sounds went away with the sponge, and the temporary fix became permanent. It does require occasional maintenance to keep uneaten food from restricting flow.
