Hmm you might be better off getting them before he gets there, IF you decide you wanna give it a go. He's more likely to accept them if they're already existing in the pond when you add him to it, rather than letting him get established in HIS territory and have him look at new fish like invaders. Just get something you won't be super crushed about if they *disappear* lol.
That being said...Tolken (my current midas) was long established in HIS tank/territory - like 2 years there by himself - before I decided to try the convicts and it wasn't an issue. Same when I swapped the convicts out for the danios.
Basically it's a crap shoot