anybody know what these could be? I first saw them on this plug when I pulled it to remove some hair algae from the base, but I’ve noticed them in a few other places in the tank now too.
That's bubble algae! Keep an eye on it and don't pop them, because that will cause to spread. I had an outbreak and emerald crabs did the trick in no time. I pretty much rented them from my LFS because I gave them back because I was scared that they were gonna nip at my zoas or mushrooms.