To run or not to run....Protein Skimmer

[Avi]

I've got my 120 going and it has 120 pounds of live rock and a sump...no bio-medium. I have an Aqua-C skimmer hooked up and it's been running all the time. I'm not sure if this is a good idea or not since it must be removing trace elements and I was wondering if it would be better to let it run on a timer...say, half a day instead of all day long. Any help with this question would be appreciated....THANKS