my gar wont stop swiming up and down the tank walls and is tearing his noseup in the process. Hes about 12in and has been doing it for ever since i moved into my appartment. I fig its the water but everything seems normal. he dosnt do it all the time, he takes breaks and hangs out at the top or bottem for awhile, and then goes a it again. He used tp live alone, without a heater, without lights, and a smaller tank, he only eats live and he used to be my freinds but this piranha bit off mostof its tail and one fins but both sortof grew back and he makes it around the tank ok