We have green tree frogs everywhere up here due to the rains at the moment!
I have never tried to keep frogs, but found this site which may be useful:
(looks like a SA business, maybe they could even respond to phone enquiries...)
Visiting the Reptile house or Aquarium at your local wildlife park/zoo may shed some light as to what frogs may like as well. Apparently frogs are more likely to stay on the rocks and sides of the tanks than swim around in water. Use clean rainwater, or leave tap water for a week to dechlorinate if re-filling the vivarium.
I love green tree frogs, they're so cute!