Other than some rock and some sand, I would give it time to mature some before placing anything "living" in it. That will allow for a greater success in what you are trying to accomplish. The "critters" can easily be transfered from some of your main tanks sand.
After a month or so, you can consider some different types of caulerpa that will aid in the export of the "nasties" in the water and aid in ph
<< is a recent thread where Hara gave some excellent reference types.