I put in some turbo snails in my tank about a week ago. I noticed yesterday that there was this black bubble on my rock where one of the snails had been. Is it an egg or something else? %
Bubble algae could appear dark. I don't think it's an egg. My snails have reproduced many times and I've never seen an egg. It's really all just speculation without a pic. I wouldn't mess with it until it does something or you positively ID it.