By "mech" I am going to assume you mean mechanical filtration (course sponge and fine filter). Yes, mechanical filtration will:
A. Keep your water column free of any free-floating particles and/or debris.
B. Keep debris from clogging up your biological filtration (bio media balls).
Honestly, I have never found "coarse" sponges to work really at all, but it depends on what you mean by "coarse". Your best bet would just be a medium sponge and a pad of fine filter floss.