I've had a betta for about a month now and he lives in a 20-gal with some little zebra danios. There are little round spots all over the inside of the glass. I'm guessing they're nose prints from the betta, but I've never actually seen him kiss the glass. The spots are too big to have been made by the zebras. Is this normal behavior or just plain weird? He seems happy and swims all over and has lots of silk plants. so I don't think he's trying to get out. Any ideas?