Is it slimy? I would take it out and rub it off, and then sit it in a 50% water and 50% household hydrogen peroxide for awhile.
There might be decaying food in the substrate causing a glump of stuff, I didn't see it. You could scoop the glob up as well and put into the peroxide mix too.
Snail eggs are a clearish to slightly tinted glob usually a circle like a pencil eraser to slightly larger to teardrop swipe shape. With little tiny dots in it. For pond, bladder and Ramshorn snails.
Mystery snails have a pod of eggs in a cluster white to pink peach color.
Assassin snails have a tiny square looking egg, and Nerite snails have a sesame seed looking /shaped egg. Both these types are individually laid.
Thinking it is a fungus growing there.