I have a 55 gallon tank, and I just introduced my betta into it, I asked my mom and she said it'll be alright since the tank is still cycling, I added him in and he's pretty happy just calm, but the huge problem is the tank has 3 mirrors made inside it, he's been flaring at his reflection for a minute now, non stop, I don't want him to get stressed I don't know WHEN we will be getting a background since my mom is busy so I don't know what I do now, I just put him in his new tank and emptied out his 1/2 gallon tank. I unplugged the filter since it was too strong, we have a small filter which will do SO MUCH better for the tank, just waiting for my mom to come home so we can set it up, it belonged to her tank she loved to death.
What should I do now? And is it very bad if he flares to long

I got him a new tank and now he can't be in it? The tank has a working heater at the moment and a lot of decorations :( Also added 2 25mL of Aqua plus which has a stress coat forumla in it and it's a water conditoner.