According to this article, a group of frogs is called an 'army'
http://www.jacksonvillezoo.org/anima...son_dart_frog/
There's lots of interesting stuff around about dart frogs, and for as little as this critter is, there is plenty of controversy surrounding breeding and keeping. Some just want pretty frogs as pets, not focussing on genetics, others are almost militant about keeping their armies pure.
Whatever your army looks like, there's no doubt that they are spectacular and appealing little critters.