I'm looking for reassurance that this part of my setup is generally "correct". Current inhabitants are a pair of clowns and an emerald crab in a skimmerless 20 gal. I run in an aq70 (from bottom to top) Polyfill (pillow stuffing), purigen, activated carbon, lastly, a bag of bio media to keep the other media in place. The polyfill gets changed weekly, carbon changed approx monthly and purigen gets recharged as needed. What do y'all think? Am I missing anything, any overkill?