greasy like buildup

[brnmeister]

Why is there a black greasy-like crud collecting in the pool skimmer at the water line? It's easy to wipe out, but what is causing it and is there anything that can be done to eliminate it?

[coachswin]

The black greasy line comes from the suntan cream used by your pool users which floats on water and tends to collect round the skimmer. A pool approved detergent should remove this quite easily