Hey guys. I just noticed that a bridge in my Bettas tank has developed a white, almost invisible white fuzz. I tried vacuuming it up, but it wouldn't budge. My betta isn't acting any different then he normally does. Any idea to what this is and if it is harmful?

Hey everyone. I'm very interested in making my betta, Oscar, a floating mesh tube, because he LOVES to hide in things and spends some time at the surface. I have instructions, but I'm wondering where you can pick up the mesh used for these. Any body know???????