They do certainly feel more comfortable in small groups, despite the fact that they do quarrel amongst each other a bit. They do not "hunt" in groups though - they are ambush predators, pretty much filling the same ecological niche as the nandids (leaffish). They are quiet, shy, retiring fish, and do not do well with more antagonistic tankmates. That being said, some more active tankmates often encourages them to be a little more outgoing, just make sure that they are getting adequate amounts of food as they're slow eaters. They do set up small territories, but intraspecific aggression is minimal and inconsequential provided they have enough room. They really do best in heavily planted aquaria with moderate lighting - bright light tends to wash out their colours. They do indeed grow very slowly, but they're also quite long-lived. Your best bet would be to grow a small group out in a heavily planted 30g with bi-weekly water changes and power feeding (feed brineshrimp/bloodworms 2x a day and have a constant supply of adult feeder guppies in the tank with them - as the guppies breed, they'll take the fry, eventually graduating to the smaller males as well).