Just a heads up on spaflex. I recently had it on my drain to my sump, however because of the distance it ran from my drain to my sump, it had a slight dip in it. It wasn't much and I hadn't thought anything of it, however, I have been fighting this noise issue for a while. Someone finally asked if I had spaflex for my return and if I did, did it have a dip in it. What do you know, I removed it and hard piped the return and my tank is virtually silent now.
Just thought I would give you a heads up.