They are in a terrarium, my original plan was let them loose but i bottled out. Greenhouse is heated to min 15C in winter. Bigger problem was summer day temps, dart frogs don't like going much above 30C, it will probably kill them. But down near the floor it rarely gets above ~27C. So far they've been from 15C to 29C and its not been a problem, in fact the little buggers are at it again today, probably be more eggs when i go and have a look. I chose Epidobates anthonyi as they should be able to cope with the temperature range, other dart frogs probably not.
I'm thinking of making a larger enclosure long term, but needs thinking about, they're good climbers/jumpers... I have a concrete floor, which can be very dry, so letting them loose probably wouldn't work too well.