Watch out who you put killies in with
I put my Aphy. gardneri in at first with some guppies in a 5 when I first got them, after the male got acculmated he chewed all the tails off the guppies. I now have a trio (mom, dad, and a daughter) in the 5 gallon hex by themselves with some java moss. They are very pretty though and often this is the tank visitors come look at (they also breed well). There are some more peaceful killies from what I heard, so do your research! IMHO they are very beautiful though. (The person I got them from after I told him they ate my guppies said they can't stand anybody prettier then they are). Maybe you could also check out some peacock gudgeons? They can take cooler temp water too. In my office I have a couple of bowls with bettas and a 2 gallon with wild guppie/endler crosses.