Milk frog vivarium size for juveniles?

[Big Rob]

I am looking at getting a small group of juvenile Amazonian Milk frogs,probably 3 or 4 and about an inch (25mm) in size.
I have got numerous empty vivs and wondered what the best size would be?

I have just bought a 60cm wide x 45 x 45 exo-terra and have got 2 different sorts of lighting hood to suit that. One has got 3 bulbs in it, 1 each of 5.0 uv & heat & night time viewing blue. Or I have an exo-terra dual unit with uv tube,daylight bulb and either 1 or 2 halogen spotlight bulbs. I also have a 45 x 45 x 60cm high exo-terra that has a custom built eco-earth type background,and have compact hoods to fit that. Or would a 45cm cube or 30cm cube be better whilst frogs are so small? I have no lighting for these at the moment though. For evening heating would a heat-mat stuck to the side of the viv be preferable to a ceramic bulb.
I will be moving the group into a 90cm high x 45 x 60 exo-terra with full bio-active substrate and custom backgrounds when they get big enough, but was thinking for the first few months.

Sorry for waffling,looking forward to peoples comments. Rob.

[elly]

I wouldn't really go for a smaller tank while the frogs are small (unless you have nothing else, of course). They may be little but they still love to climb around and they need space for that.