I think it's cause your changing them around constantly, he also looks to have a slumped case of fin rot from the change in temp being so constant and going from big to small o_o ... I know from how he looks that he isint dieing incase your worried about that ^^ but rather he's pretty pissed off and it's best to put stress coat in the water for behavior help, also keep him in the same aquarium for a week with no change what so ever * even in his food* so he can get back to a normal existance for a betta. Mine always flared his gills and danced while I was around o_o thats what the picture I posted up there was from cause he spins at me. Most likly it's just a action like a female betta ^^ if I where you I would feel flattered sweetvegan lolc your big mamma fishie =3.
Afor his tail and everthing in the before and after pictures o_o Other then his bottom fin he just looks a tad clamped, but thats bound to be expected, how would you feel if you where moved from one tank to another and then another and another? It's like moving without any of your belongings four times O_O. Think of him as you would think of yourself and most likly your best conduct will help him more then anything.
Cause at the moment he looks really stressed out in that image and he just needs a staple home, and bettas do not by all meens need a 25 gal all to themselfs, even two bettas with a davider dont need more then 1 gal and a half to themselfs O_O in ether situation your bettas would both be much happier with a davider ranging from 1gal to three gal from the walls of the aquarium and on ether side so they are at least 14 gals away from eachother causeing a blind spot that they cant see eachother. Then have a school of nine or ten females in the center of the daviders but away from the males for calm relaxasion of female learing and a more less depressed lifestyle.
Buying a second 25 gal is more then extream=3 so good idea on your next saving object. I have a 1.66 gallon that a betta lived in for a long time and he was the happiest I've seen, then I have seen at many breeding places a betta with only a half gal to themselfs in Ball canning jars. So 25 gals is always abit overload for any betta O_O mine sould only use 5 % of that XD even with plants, all together you can hold with four daviders and a cener area. Anywhere from 4 males and 18 females to a 13 davided aquarium with a male and female in each davision.
