If it's a standard 33gl (footprint wise), then I would go with green neons, or better yet (in my opinion) Black Neons. I find a 33gl not quite long enough to fully appreciate Rummies, plus Rummies are way to ADHD for a tank that size, in my opinion. Don't get me wrong, I like Rum, ahem, I mean Rummies, but yeah, I wouldn't really go with them in a tank with that footprint.
No, it is not a standard size. It is 24inx18inx18in. I thought I would keep 9 rummys, 3 otos, and 2 Apisto. I don't have the tank. It is out of stock but I have everything else.