I agree that looks like bubble algae, but what’s throwing me is it’s blue. I had green bubble algae that looked like that.
If it’s the same thing as green bubble algae, it’s a pain. Green bubble algae does well in good water conditions, so it’s hard to starve it out.
I did finally get rid of mine, but I have no idea how. I did big water changes, seachem phosnet, manual removal with tweezers, emerald crabs, and probably other stuff.
I’m not sure if any of that helped, all of it helped, or none of it helped, but eventually it wasn’t in my tank anymore.
If it’s bubble algae, get used to dealing with it for a bit as it doesn’t go away quickly or easily. At least, it didn’t for me.
Conversely, it’s not that bad of a problem. It’s not really unsightly per se. Except for the possibility that it will tank over the tank, it doesn’t really matter that much.