I've had my 20gal tank set up with fish for about a week now. All I have currently is 10 neons. Well I woke up this morning and it almost looked as if they were fighting? They were swimmming around chasing eachother, and when they're not doing that they're swimming up and down the aquarium walls. I have no idea what's going on inside my tank. I did a water change while siphoning yesterday, and tested the water. Ammonia 0 nitrite .25 and nitrate 0. Help?