It is my moms fish.And he is heka big and he was in a small tank.But my mom got to Chiclets and got a big tank.Then one night the big fish could no breath so she put him in the big one with the Chiclets because maybe his tank was to small for him.But any way.Later on he lived and the Chiclets were beating him up so my mom put him in his originally tank.Then in the morning put him back in the big one.then that night put the Chiclets in the small tank and the other fish[koi] in the Chiclets old tank.So then one Chiclet got stuck behind the filter and died.Then She had another fish outside and put him inside with the koi.And like they are always kinda together are they mating or what.All of a sudden i found out the koi's back fin [but area]was changing colors like peach or orangish.Is that a sign she or he is pregnant or what.Or does he have a diasase or something.Is he/she Ok..Thank$ for the help.