Lol I would've have my ¢2 on the subject but I have yet to take the plunge into nano tanks. My water is just so hard it really limits me on what I can keep. If I had to pick a nano fish for this I think I would go with the stone catfish, gets to roughly 1-1½in max size if I remember correctly. They kinda look like a banjo cat but smaller and more grey instead of brown.
P.s. I tend to like more of the south american variety of nano fish so that's why I haven't really taken the plunge into that aspect of the hobby just yet. Lol once I get my water sorted out for good then I might.