Hi Tanzee,
That dude at the pet store deffinetly knows what he is talking about. Most species of frogs won't hesitate to eat other small frogs. In some species of frogs most of their diet is made up of other species of frogs. Whether your tree frogs would eat the new additions depends on the size of the frogs. If small and large means a 1 inch green tree frog and a 4 inch cuban tree frog then there deffinetly is a large risk that the smaller frogs would be eaten. Most species of tree frogs can easily eat anything that is the width of their head or smaller. Some species can handle larger food items. When there are multiple frogs in one cage it is safest if they are all the same size.
The other thing I want to touch on is mixing species. In general different species should be kept in different cages. Occasionally some species of tree frogs will do well together in the same enclosure but it's risky. Consider the conditions that both species of frogs need to live well. Are they the same? Probably not. Have a look at www.amphibiancare.com/frogs/articles/communitytank.html Good luck
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Devin
devin@amphibiancare.com
www.amphibiancare.com
4.1 Dendrobates tinctorius 'Dwarf French Guiana'
1.1 Dendrobates tinctorius 'Powder Blue'
5.1 Mantella aurantiaca
2.1 Mantella crocea
0.1.4 Mantella madagascariensis
1.0 Ceratophrys cranwelli
1.0 Bufo americanus
0.0.1 Salamandra salamandra
1.0 Ambystoma tigrinum
0.1 Chamaeleo calyptratus
0.1 Phelsuma dubia
1.1 Uroplatus ebenaui
0.0.1 Chrysemys picta belli
1.0 Terrapene carolina triunguis