Can xenia remonve phosphate and nitrate?

It's near impossible to control where this stuff is going to grow.It can release single polyps which will start another colony somewhere else in your tank,often where you don't want it.If you were near Jersey I could give you plenty.If you want something to cover the rock pillar I think I would try star polyps,grows fast but much easier to control.Since the star polyps grow on a mat you can easily tear some off to remove them or glue some where you want them.

 

Shackmel's parents secondary form of filtration (behind the protein skimmer) is Anthelia harvesting. Her mom feeds HEAVY 3 times a day. Since we know she's not ever going to change no matter how much we explain that this is a mistake, this method works well. After a period of time, a rock that is completely covered with Anthelia will be thrown into a bucket in the garage. Then a new rock replaces it. I don't even want to think what the nitrates would be if this method of nutrient export wasn't used.

I think you'll find this article useful. The Food of Reefs, Part Seven: Dissolved Nutrients by Eric Borneman - Reefkeeping.com