You'll likely have bio slime regardless of what you feed the fish. It should come off easily with a scrub brush.
another question. While the system is running, how do I clean the tanks. How do I clean the FT from the bio slime. how do people do it? Do they transport the fish to another tank, clean the main one and then put the fish back? I really like to know. thanks
My guess is they don't, other than brush-scrubbing observation windows - no soaps or chemicals. I haven't cleaned my tank in the five years my system has been running. One thing to keep in mind is that all wet surfaces in your system are part of the bio-filter so, other than aesthetics, there is no reason to clean the fish tank.