Regarding the above, I do not recommend this type of set-up for firebelly toads. In fact the only water that the toads will have is from a shallow dish that is at least 4 inches deep. To provide them with water that they will need for swimming and drinking, put a reptile bowl that is at least 4 inches deep, filled with water on the floor of the tank. Make sure to put a rock in the middle so that the toads can get back out of the water once they are done. This type of set-up is easy, regarding feeding and maintainance.
Proper equipments is essential for maintaining healthy active toads, or any animal for that matter.
A heater may or may not be required for certain set-ups. I will list the set-ups and whether or not they require a heater. Depending on the temperature of your house, a heater may not be required at all, a room temperature of 70 F or higher is fine for firebellies. Anything lower than 70 F and heating may be necessary. Depending on the size of the tank used, a heater may or may not be required.