If you have any chance of water in your skimmer a Gizmo isn't a bad idea. I do NOT use one because
a) I use an AquaDor cover over the skimmer
b) I lower the water below the skimmer
c) I remove the pipe going to the skimmer so the bottom of it is open to drain.

Only once have I found any ice there, and immediately poured in hot water to clear it.