Tonga is near the eastern edge of G. smithii's range and I have not seen a collection from there, but it is possible.
With good cavities, it is possible that several animals could coexist for awhile in a 10 gal., but over time you would probably lose animals as they molted, etc.
It is actually easier to keep different sized mantis in an aquarium than same-sized beasts. With a size range, animals will sort themselves out according to cavity entrance size. Big animals can't get at small ones. However, I am talking about natural cavities that they would live in, not pieces of pvc that do not have restricted entrances. I think the most stomatopods that I ever recorded from a single piece of coral rubble was 23 in a piece not much bigger than a breadbox. This was in Panama where N. bredini and N. oerstedii are extremely common. The size of animals ranged from 9 to 66 mm with about a dozen being over 30mm. This was only possible because there were numerous cavities of different size.
Roy
