I got my blue crowntail guy into my community tank!
I have three adult male bettas. I previously gave each one of them a trial run in my community tank but each one got a failing grade in "plays nicely with others" and had to be removed to a private tank within minutes. But, I really wanted to get one into the community tank. Any one. (I have enough tanks.) So, I put my blue crowntail in a small tank with one opaque side and put it near but not next to the community tank, on a slight angle so he could maybe get some glimpses of other fish (not bettas) but not stare at them. Over the course of a week I slowly rotated his tank until it was parallel to the community tank, then moved it next to it, so he could see right in. Tonight he got moved in, and he's not flaring at my other fish!

He has been in there all evening and is doing great, I think he has a new home.
The other fish:
One plain yellow guppy
One black molly
One dalmatian molly
One glow light tetra
One plain boring tetra
Two spotted cories