Moss bubbling?

So I bought some xmas moss in with the hopes of attaching it to a stump and making a tree lol But until the tank is free from goldfish I just put it in a glass and left it on the windowsill to hopefully grow and heal up from transport. I looked at it today when it was sunny and there were quite a few bubbles on the top of the water. There is nothing else in the glass and its been in there for about a week but just today I put it on the windowsill... what does it mean/is it good or bad?

Ok thats what I thought but I just wanted to make sure it didnt mean they were getting too much sun.. I want this thing to grow! lol

Lol yea I just want it to be thriving and healthy since the tank it will be going into will be low-light (standard 10gal lighting) but it will at least be up high. I read it makes a cool tree-like appearance when attached to driftwood so I thought itd be a cool thing to try. if it doesnt ill just have a mossy log anyway