I'd start with a real life distribution chart of where these animals live and breed naturally.

European Fire-bellied Toad - Bombina bombina : WAZA : World Association of Zoos and Aquariums

Eastern Europe from the coasts of the southern Baltic Sea south to Turkey and eastwards to beyond the Ural in Russia. Reintroduced into Sweden in 1983 after it became extinct about 1960.
Then you need to work out the average temps in summer and winter. Only do this for 1 location. Say Turkey.

Turkey Average Maximum Temperature Chart

this chart is your guide to how hot the tank should be on a monthly basis.

After that the rest is habitat, and lighting.

And the final piece of the puzzle is the animals themselves sometime they will simply not want to breed.