After much deliberation and research, my boyfriend and I decided to buy two dwarf puffers. They're currently residing alone in our 50g tank until we can get their 15g set up. (My boyfriend, who used to build houses and has built a ton of stuff in our apartment, is installing a shelf for their tank.)
I've already fallen in love with them. They're the fattest little things and just hover craft everywhere. :3 They love the moss ball in their tank and always hang out together.
We have named them Herp and Derp.