The skimmer may help with the DOC
and organic phosphates
but not really the inorganic. You may need a PO4
sponge to really get things to zero. The same can be accomplished with regular water changes if you are using a pure water source such as RO
Also be wary of over using dried and flake foods. They are lousy with PO4
's but can be diminished by presoaking in RO
water and discarding the water before feeding. A variety of different food sources will also help. If using meaty foods, avoid the grocers. Many type of fresh or "fresh frozen" seafoods contain tri-poly phosphates which introduce basically the same thing. When possible buy live but I find some "pre-mades" better than others.