Brown layer on top of my water

[Diomedes]

A skimmer won't help here at all unless you feed its chamber via an overflow (the most effective use of it anyhow), but since you don't have one (thats cool too) use a fine mesh net (blue handle, white net) and scoop it out. I think it is a collection of oils, detritus and brown algae. All it takes is a small clear film of oil to develop and that can provide a medium for algae growth on the surface. Look through your tank and up when netting it out to make sure you get most of it. It will lose intensity as your tank matures and you maintain your tank at scheduled intervals. Some parts of your rock might be uncured, or too much oily food additions (Mysis IMO and exp.) may cause it.

Good Luck

Stephen