Thanks for the help, much appreciated.
He(/she) is not a goldie, he's not a bala shark.
I'm inclined to agree he's a cyprinid of some kind, but maybe a rasbora rather than labeo? I don't know! Pictures on the web to look at are thin on the ground I'm finding.
Here is a better picture of the same fish. Does it help?
I've been studying him a little more, and might be able to give more detail than the pictures can. He's about 2" long, with relatively large eyes. The mouth is towards the bottom of the face almost pointing down but it's tricky to tell, and has tiny tiny feelers like a catfish or loach (but much smaller and thinner, you can barely see them). He has rows of dark spots running along his body, getting lighter as you deviate from the boldest across the middle
Seems to be eating flake food, and avoiding bloodworm and daphnia. Lives in the top 1/2 of the tank. Seems to have quite a flat bottom profile to his body (not flat like a plec, but certainly not rounded like a danio or goldfish).
He seems very healthy in as much as I can tell- eats well, is active but not manic, and has perky fins. Was bought to match the specification that it "won't eat anything else in the tank" apparently. This fish is not hassling anything, and is getting hassled by nothing else.