Help in identifying a couple of things in Tank

Hi all, have been a long time lurked on the forum but this is my first time posting. Love the forum and it has helped me loads in getting my yank set up.

I've had it going for about a year now but have noticed a couple of things that I'm having trouble identifying.

Was wondering of any of you guys could tell me what you think the black/grey jelly looking think starting to creep out from under the rock is?

I have something similar in the second picture in the crevice.

Thanks so much for your help.