I have "cold" room temperature 7 gal tank w/ a paradise fish, 2 red cloud minnows, and a hillstream loach going on a year now and it's a great low maintenance setup. A big Anubis and a few stems of hygro round it out.
Red clouds are amazing by the way. Very active, great colors. The Paradise fish (female) is the boss of the tank. Hillstream is a decent algae eater and leaves the plants alone.
Good luck with your setup!
Dont run tropicals like barbs or tetras in an unheated setup, they will get sick and die eventually.
Smoke 'em if you got 'em.
20g Tall Low Tech Planted