They definitely are interesting to look at. My first post on this forum was about them as I had no idea if they posed a threat. Luckily I had no fish then. But I left them and still had them after I put in betta, 5x ember tetras, and amano shrimp.
I found a name of "Ciliate Zoothamnium arbuscula"
I found a name of "Ciliate Zoothamnium arbuscula"