Split personality

[SkiTheBerks]

Since I put my Betta in the new tank, I have noticed a behavioral change. He seems happy swimming around from side to side and top to bottom, seemingly to enjoy the plants and also loves to hang out in a little alley on the left side of the filter motor housing. When the tank light is on and the room lights are on, he is "normal" doing an occasional flare. He loves to chase after the food and strike at it like a little piranha.

However.....When the room is dark and the tank light is on, my fish reveals is true aggressive behavior. He must think nobody can see him. He swims from side to side flaring up at each side and seems to attack the thermometer and the heater. I can understand the thermometer as he probably sees his reflection in it. It is quite entertaining to watch him protect his turf.

Once the room light goes on, he reverts to this calm and peaceful fish! It is unreal.

Will this harm him by letting him be aggressive? I can easily put a room light on a timer to coincide with the tank light so there will not be a dark room and tank only light on.

[accountingchick]

My Little Charlie does the exact same thing. I think that it is because they can see their reflection on the tank when the room lights are off. I would recommend that you get the timer because it is not good for him to be flaring for long periods of time. I just always make sure that I always have a room light on when his tank light is on. I do however though use this method now instead of the mirror for his flaring time. I will wait until it is dark and then I will turn the lights off for five minutes and watch him go. It reminds me of a boxing match because the instant that the bell rings, boxers start fighting. Well it is that way with Little Charlie, the instant that I turn out the light it is fightin time.