Thanks! I'll look these guys up.
I tried a giant plakat betta - he was considerably bigger than the rainbows. They never went near him, but their activity made him a nervous wreck and I lost him - broke my heart, he used to let me pet him. So, I tried a paradise fish. The LFS guy was a huge fan of them and assured me he'd be fine with my rainbows. Not so much - he attacked, he lives at the LFS now.
So, I'm a bit gun shy.
I'll have to go to the store and watch some loaches. I'd like something that is a bit quieter, activity wise, than the rainbows. Any more fuss in that tank and it won't be relaxing to watch!
I've thought about an angel fish, is that an option? I wonder if it would limit my choices from there too much.