pest

I just wanted to no if anyone has seen this before or have any idea what these are.? They don't move so I think, but I noticed one of them on a rock months ago and now there allover my rocks. I just want to make sure it's not a type of worm that could harm my fish bc my arowana has been acting...

Hello all, I've recently discovered that Ive got some sort of worm thriving in my aquarium gravel. I don't think they are harmful to the fish but I dont want them in my tank cause I think its been turning some of the fish into picky eaters. I started noticing them a couple months back and to...