This. It's stressed for sure.Looks like a rainbow to me, just stressed.
What's the max size on Rainbows? I have 3 of them atm, currently about 3" eachMine was not a hybrid, they just go thru many color changes in the course of a day.
It had just been fished out of my 400 gal kiddy pool pond, and put in a relatively bare tank. Here are some shots of the same fish.
It was interesting to me, that after being kept in the kiddy pool with lots of space, they seemed to become more elongated, they had grown up in a 75 gal, from 1"