Tanichthys Albonubes...White Cloud Mountain Minnow..A very pretty fish.stays small (under 2 inches) is very peaceful.easy to care for.not picky eaters.even easy to breed if one is so inclined.doesn't really need a heater ; likes temps in the low 70s down to the low to mid 60s.
How big is your tank ?
What kind of filtration are you using ?
I second Lohachata's suggestion. White Clouds are great, though they are schooling fish so for best results you should should get a group of them. 5-6 should be sufficient. Let us know what you end up getting in the long run! Also, it is important knowing your tank size, too, because if it's too small they won't have room to swim around. Shoaling fish exhibit better behaviour with lots of swimming space. (Please correct me if I'm wrong, Mods)