I have a Fluval flex 15 and opted to get a canister filter for better filtration and to be able to utilize lily pipes. The problem I am running into is now that I have the lid off of my aquarium, so much crap is flying in and sitting on the top where the canister can’t get to it. I also feel like water is starting to stagnate in the back sump now that I have switched to the canister. I have a lily pipe and a surface skimmer coming tomorrow. Will that help with the surface debris? Should I somehow close off the back sump to prevent the water from stagnating?