Even though they are not usually considered "beginners' dart frogs," a tall tank like that with some bromeliads on the cork would harbor about 4 very entertaining D. imitators, or one of their close kin such as intermedius. These thumbnail arboreal fellows get along in groups relatively well, albeit with some non-fatal arguments among the girls in particular, and are as hardy and easy as the larger recommended "beginner" frogs such as leucomelas and auratus. The only thing that doesn't recommend them for a beginner is their tiny size, which can be rather intimidating, and their propensity to escape faster than a speeding bullet, which requires lots of attention and a well sealed top. But they also have the advantage of being able to raise their own young without your help, as long as you have bromeliads with water filled axils, which can be a great show to watch. You're chance of getting at least one of the opposite sex out of four unsexed juveniles is fairly good.
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Patty
Pahsimeroi, Idaho
4 D. auratus blue
5 D. galactonotus pumpkin orange splash back
7 D. imitator
6 D. leucomelas
4 D. pumilio Bastimentos
4 D. fantasticus
6 P. terribilis mint and organe
4 D. reticulatus
4 D. castaneoticus
2 D. azureus
4 P vittatus
2 P. lugubris