my oscar is acting very funny... about a week ago i did a water change and had to use tap water, next morning i walked by the tank and he FLIPED out... went from one end of the tank smacked into the other then back to the otherside, an so on, the only thing that stoped him was the heater. about 2-3 days ago he started to act normal again, exept for when he trys to get something to eat. he goes up to the top of the watter then starts biting at something, gose back under water fliping in circles. sounds like to me his swimblader is screwed up. any idears on what it could be?