I agree with all the above, and I also do not worry (too much) about phosphates and nitrates. I do sporadically test for these, but I do so in order to put them into my spreadsheet for record purposes in the event that anything goes drastically wrong.
My corals always exhibit increased polyp extension after I stir up my sand bed or blow off the rocks, and, to me, that indicates that they are getting some form of nutrition from the detritus.
Plus, I use tap water for WCs :0