That did look a little odd. Do you have a sediment filter on your incoming water? I am wondering if there is something that floats coming in. Maybe a child dropped a piece of cookie in there. Or maybe something is growing. I have very limited experience. Maybe somebody has seen something like that before.Look at the pictures I posted. I was thinking of cleaning the brine tank since its low on salt. Do you still recommend I wait?
Anyway, your deposited scum seems to have been from something that floats. I think of stuff that sinks when I think of cleaning the brine tank. "What I would do" does not go as far as a recommendation. I might fail to do the right thing at times. But that might be enough to get me to stop adding salt and clean when I am about out. If the salt will not completely cover the water, I like to tilt my salt to have some salt out of the water. I don't know if stratification is a real problem, or not, but tilting would seem to make sure that won't happen as your salt gets used.