i have a 5.5 or 6.5 fluval edge tank. ive had it set up for about 2 or more years now, with the same fish in it ever since. i think i either started out with 8 or 11 "boraras maculatus". but now i think i have 7. they've been AWESOME fish, and never seemed to not like my tank. they are soo small, and even at full grown they arent even half an inch. and yes, they can be really that red if you take care of them.
i think once they all pass away i may get a betta. or find some other micro-sized fish for it.