I like that set up - very nice!
Anyways, I have used a "250 gallon" heater for an 80. It literally is not the wattage, but rather that it does the job. I find it hard to squish a heater in anything under a gallon xD As long as the heater is adjustable and you have a thermometer you should be fine. Test the heater first in there, adjust it as needed, and there ya go.
Breed for the breed, not for the money; the words any REAL breeder would understand.
You must know nothing in order to know all, for all is nothing and nothing is for all.