Please Help - are my frogs too cold?

[Wendy]

Hi,
I'm having a bit of a melt down as im afraid my Green Tree frogs' are getting too cold at night. I'm in perth and our winter is setting in. They have no heating as such but a double light canopy with two repti glo 2.0 UVB lamps. This is only on during the day and when I got up this morning their temp was showing as 67 deg.

If this is too cold (and I think it is) how would I go about heating them at night? This is my first winter with them.

I have 3 green tree frogs
Exo terra 24x18x18inch terrarium
They have a water fountain and large water bowl
Their substrate is stones (not small, so they dont eat them)
They eat gut loaded crickets (dusted)



Please, any help would be greatly received. I did ask at my local pet shop but I felt they were just trying to sell me what they had, and not necessarily what was right for my frogs.