So, I got 6 neon tetras yesterday. They live in my 10 gallon by themselves. Yesterday, they were schooled tightly together, trying to get used to their new home. Late last night (about ten) I noticed that two of the neons were swimming around almost as if they were night guards while the other four were sleeping. Today, the "night guards" were tumbling over each other, fighting. Could anyone tell me why? My fattest neon seems to wander away from where all the other neons0 are and rub his mouth/nose against the tank's glass, like a male betta that saw another male. I don't think he/she has the neon tetra sickness thing because he/she is very active and when I fed them, she/he ate happily. Is this normal with neons? If not, what should I do? My ten gallon is cycled, filtered and heated.