I have a 30 gallon tank, which I pretty faithfully done weekly 10% water changes; but I keep getting nitrates in the 20-ish range when i want them in the <5 range.

Any suggestions? maybe someone with a similar tank size will have some insight on this.

Stats:
Life: pair of o.clowns, neon-goby, bi-color blenny. skunk cleaner shrimp. 4 peppermint shrimp (got rid of the aptasia ). large feather duster, some xenia, 1 mushroom, and 1 Kenya tree; some cheato in the fuge.

Stuff: lots of live rock (not a clue on the weight, but as much as i can fit and still have swimming room for fishes), 4+ inch DSB, hang-on skimmer, hang-on refugium (small), eheim classic canister.

Basicaly I'm thinking to feed less and maybe take the bio stuff out of the canister filter. but i was curious if anyone else had insight.