Sponges, or Something Else?

[Hugh Mann]

This roughly snot yellow/green sponge like crud has been growing all over the walls, rock and equipment in my improvised tank here, and am wondering if you good folks can ID it for me. And whether or not it's good, bad or just ugly. Thanks.

 

[ichthyogeek]

Probably just ugly. If it's snot yellow/green, then it's probably photosynthesizing, or eating a ton of phytoplankton.