I need to add about 2 lbs of CYA and I've read that some people put the CYA in a sock and place the sock in the skimmer until it dissolves. Two questions about that: is it necessary to use a sock? Could you just pour the solid CYA in the skimmer and let the sand filter catch it where it would stay until dissolved? Second what kind of sock is used - panty hose or a plain cotton sock?