Hello and welcome to FF! If using real plants recommend ABG type soil for substrate. If not, shredded coco mixed with dechlorinated tap until damp and clumps in fist without dripping water out. You will need a layer of plastic window screen between the leca and the soil; otherwise they will mix. Also, access to leca layer for purpose of removing excess water should be available.
Can't use heat sources under substrate since frogs bury to cool down. Heat mats have to be affixed to sides and they tend to be less efficient that way. A dome with inline dimmer and a 60 watt Ceramic Heat Emitter alone or in combo with heat mat might work for you. Keep 80F (27C) during day and 70F (21C) at night. Good luck

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