Since Those Who Know haven't yet shown up, and usually do just as I'm offering an an amateur opinion, I'll trigger the phenomenon by a bit of a Google.
http
/www.funadvice.com/q/goldies
This offers a bit of info about temperment - much too rare an addition.
and with a tank full of goldies, heavy planting for privacy, etc. becomes a bit tricky.
This is referring to ponds but:
... Rosy Red Minnows:
Almost a miniature version of the Orfe in appearance, the Rosy Red Minnow is a useful pond addition for exploring tight nooks and crannies in a well-planted pond. They are a shoaling fish, and can become very territorial come breeding time, the Minnow is one of the few carps to show aggression. It's a good job it's such a small fish! ...
http
/www.####comfish.html
This has a few more suggestions, with an important caveat regarding otos.
Would like to add to that that plecs and loaches need even more than some clean water conditions, despite their notorious addition to the brew; it's unfortunate that goldfish are such little poop/ammonia factories.
Also:
http
/www.gomestic.com/Pets/Fish-Compatibility.35819
... Goldfish have a category of their own because they are unpredictable. Generally they will nip on fan tailed Goldfish or other slow moving tail fish, which is why it is best to keep them by themselves. They do not have problems with Coi (Carp) fish. ...
If yours aren't aggressive and have a very large tank with lots of concealment spots, and the water quality is kept very high, I suppose native minnows may be a possibility.
I have a Central Mud Minnow, who survived being dug out of a drying mud puddle.
They are a hardy, attractive cool water fish, and I did come across a site where they were listed for sale but can't seem to find this right now.
But if you want to find out if any potentially compatable native minnows are available and whether they are, you might try;
http
/forums.pondhobbyist.com/forum.php?catid=22
It would be awful if you tracked down some such fish and it turned out not to be happy or safe, but these people may be able to find some attractive, cool water minnow that's perfect.
Lotsa luck