I am using Poly Filter Pads in my 150 gallon reef tank. I am really pleased with this product. It’s really easy to use and can be cut to easy fit your sump. They are great at removing just about anything harmful (but it’s not a substitute for carbon). At first, they turn dark very quickly but after a few changes, they will last longer (up to a month in my tank). They keep my water clear (no yellowing).
Unfortunately it’s a little expensive to use Poly Filter Pads on a regular basis. I now keep some just in case I need but I have stop using them all the time. Actually, I have been using the same one for over a year. I simply rince it really well and let it soak for a good week when dirty. I am not sure how good it is but it works fine for me.