Join Date: Sep 2010
Location: West Hollywood, CA
In a 10 gallon you can have a school of 12 or so microrasboras (phoenix, chili, maculaus, sparrow, etc, there's a zillion but the chili ones, boraras brigittae, are the most colorful) or microdevario kubotai. Ember tetras are another option if your water is pretty soft. All of these fish are really tiny, under an inch.
You could also do celestial pearl danios but I don't know if they actually school. In general, for fish to school you need to have a bigger fish in the tank. Fish only school when there's some sort of danger present.