slimy

This white film on the cord of my uv sterilizer and other cords in my fish tank, what is it? I'd assume it to be algae. I've had this in freshwater tanks before, I believe. It comes off very easily and feels slimy. Just want to know what it is, is it good or bad, and how to minimize it or get...

I've had this film/tubey structure encasing this rock for at least a year now, and I'm beginning to get curious of what it is. When I removed the rock from the water when transferring tanks in July, the film felt slimey but did not readily brush off. It seems to be inflated almost like a halo...