Biocube 29 nitrate issues

[acepumping]

hey, i have a 29 biocube, with light on back of tank and all the right stuff for the tank. carbon floss, phosphate floss, rowa, etc, took out the bioballs because i heard they were garbage, i have a few rocks in the back middle chamber,i have the little skimmer that you can get with it, 2 small clowns, 1 blue hippo, 1 goby, 1 flame angel and 1 stupid damsel, all small size. and about 15 corals.. besides doin water changes how can i go about removing nitrates?? whats the best macro algae to suck up these things in the back, i have tried that cheatah stuff but somehow it just disappeared lol.