Carniverous plants require, for the most part, acidic soil and this is not something you can easily provide in a vivarium without harming the frogs.
Mantella habitat does not have an abundance of carniverous plants, so there is no reason to have these plants in their tank.
What kind of mantellas did you get?
For more information
Devin Edmundsmantella.amphibiancare.com/ and
www.freewebs.com/kapoktree1/mantellacare.htm
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A room of herps.
www.freewebs.com/kapoktree


