Hello and welcome to FF Chris! This is an excellent article about FBTs: Frog Forum - Fire-Bellied Toad Care and Breeding - Bombina orientalis and relatives. The ExoTerra and similar front opening enclosures are more expensive than a similar sized aquarium; but they are way more convenient. That is due to the front opening doors, front to back ventilation, and no need to remove lights and top mounted equipment during maintenance. Myself would go with a 18x18x18 cube for the FBTs since they will have lot's more area to play with.
See that you are using moss as substrate, so want to warn you that if frogs feed on it; it's an impaction hazard. Good luck!