Green tree frog help?

[AussieReptiles10]

I have just recently acquired 2 large adult male green tree frogs in a 18'x18'x24' exo terra terrarium and i was wondering if i bought a new green tree frog or two would it have to be as big as them or could it be smaller and if i buy a female is it ok to have her with two males? If i do get more i would probably get 2 and i probably wouldnt know the sex of them so it could be 2 more males it could be 2 females and it could be 1 of each i was just wondering if it is ok to keep them alltogether and do i have to get frogs the same size as the ones i have now or is it ok to get smaller ones?
any help appreciated, cheers

 

[Jimbobulan]

Never put anything that can fit in their mouthes, unless you want it to be eaten.

 

[AussieReptiles10]

So it would have to be about adult size?