It looks like a live healthy bacteria culture. Maybe I could just clean up the feces and uneaten food off the bottom.
In my circular fingerling tanks, where I preclude centripedal flow because they can't take a lot of current, I use a fine mesh aquarium dipnet attached to a section of 1 inch PVC to reach out slide along the bottom to pick up feces and uneaten food. I dump into a five gallon bucket. Works quite well. My center mounted membrane diffuser puts most of it into a pile next to the center.
I'm working on a DIY plug in siphon powered by a small pump, as I'm not impressed by the siphon's aquarium owners use. And I don't need to buy an expensive pool or koi pond vacuum.
