Husker your going to loose trace elements through skimming, but in saying that your going to loose them through the use of most filtration methods. Also with most trace elements we dont really know what effects they have or if they even have an impact. That and the fact they are just "Trace" means that no matter what their effects are minor at best. I find to just make sure your on the safe side to find a good grade trace element suppliment and dose very infrequently to cover your bases.
The one thing we do know however is that detritus and similar gets produced 24/7 so best to keep filtration running at the same basis.
Mojo