Used a brass check valve, didn't go well.

[Clooney]

Ended up getting some cuprisorb, gunna run that for a long period of time and try a invert in a few months and see what happens.

[maron6977]

I hate to say it but I did a similar thing . About 5 years ago I install a brass gate valve on my return . It took about 3 days & knew something was wrong when my brittle star's body's started exploding . You can recover !!! It'll take time , something to absorb it & water changes .
Good luck