help identifying something in tank

I have a betta I've kept isolated in a small tank that I think is constipated because it isn't eating. I've been waiting and still am waiting for a bowel movement. In the meantime, I keep finding something in the tank in small amounts which should otherwise be clear and spotless. It looks like a small fuzz (like pulling off small parts of a cotton ball all stretched out) which is white and isn't anchored to anything that reappears even after I remove it. Is this just dust or something? I don't have a filter in this tank.

i haven't fed the fish anything since the reason i isolated it was b/c of its constipation. it's fasting. they're really small though. I don't want you to get the wrong idea.

that's what i'm hoping but part of me doubts that very much.