I'm considering getting a 3D background for my new 75g cichlid tank. However, I am concerned about what goes on between the background and the glass. Has anyone had one set up for a while that can share what happens back there? Does waste build up back there, should I expect an ammonia spike in the future and a tank full of dead fish? I understand there are ways to keep water flowing, but that doesn't necessarily keep it "clean" from decaying waste. Any tips?