Betta Changed Behavior

I got a V-tail betta. He usually swims in my 30 gallon tanks with 3 mickey mouse fish, a few dano, a moontail betta and a few tetra that look like ghosts. They usually are fine with plain tap water, but recently the tap water was pure white so I added some Fresh Start. They started acting weird like they are trying to get air so I move them to my 20 gallon tank that has 5 tiger barbs in it. The other fish returned to normal, but my V-tail betta went into hiding under my filter. Just to be clear I know the 20 gallon is overloaded I'm just waiting for my water to return to normal, so I can place my fish back in the 30 gallon. My V-tail betta usually swims around not caring about anyone in the tank.

 

What are your ammonia, nitrite and nitrate levels?

 

He's in a new tank with aggressive fish like tiger barbs that will likely attack him and nip his tail. I would first see if he is hiding because he is being bothered by the aggressive fish. He is probably very stressed.

 

they swimming near the other end or middle. no where close to him & when his tank was good he had 2 other aggressive fish but didnt hide. He usually hangs with a red tail shark which suppose to be aggressive and a halfmoon betta but he acts like he dont care about them. he not even flaring his gills like they threatening him.