Sounds like you’re ready to me too!
Anemones need about a least a 6 month old established tank.
In a 125 you should be fine. Powderblues are beautiful but very, very delicate. If you can do it place it in a QT tank by itself. They are prone to ich when stressed, and they stress very easy.
Acclimate very slowly and keep its life very quiet for at least a couple of weeks to get used to things. So do your water change BEFORE he is introduced so you won't have to do it during his adjusting time. Make sure nothing chases him or spooks him. Make sure the lights come on slow...do everything slow around him.
Those first weeks are critical. Most powderblues die within that time frame. You want one that has been in the LFS for a while. Otherwise it is going from shipping to your house, and that’s allot of stress. At my LFS, I offer to pay for it, and then wait to pick it up. They mark the tank sold and it is in a QT all on its own before I even bring it home.
Some stores will do this and some wont, sometimes it is a matter of space, but most times powderblues just don't last so the store wants to sell it fast. An owner of a fish store actually told me this.
