Housing
Horned Frogs are known to eat other frogs - even their own kind - and should always be housed alone. These frogs should be housed in a 10 gallon or more aquarium with some kind of non-chemical, unedible substrate they can burrow in (never use cedar or pine shavings, gravel, astro-turf, bark, or sand).
Provide a large, shallow water bowl with a water depth enough to cover half the frogs body. The water must be dechlorinated before your frog comes in contact with it; you can use drops or let the water sit out for 24 hours before using.
The aquarium should be cleaned and the substrate changed once a week. Use hot water and a paper towel - no soap.
Temperatures
Daytime temperatures should be between 80-85 F; temperatures at night should drop down to 70-75 F. To accomplish these temps, incandescent heat lights can be used. Never use heat rocks - they will cause thermal burns on your frogs delicate skin!
Horned Frogs will occasionally hibernate when their cage temperatures become too hot or cold or for other husbandry problems. Correct what's wrong and, as long as the frog isn't losing body mass, be patient: it will come out of hibernation on its own.
Diet
Horned Frogs should be fed mainly crickets dusted with reptile vitamin powder. You can also offer adults gold fish, baby mice, and mealworms. When offering dead prey, use reptile tongs to prevent substrate ingestion. Remove all dead or uneaten insects from the enclosure daily.
Escapes
If your frog is cut or burned by something in its cage, remove the object and call a vet before applying any kind of medication - some antibiotics are lethal to frogs.
Fungal infections are very common in tadpoles and younger frogs. They look like inflamed areas of the skin surrounded by whitish threads. In its early stages, it can be treated by immersing the frog/tadpole in a 2% solution of malachite green or Mercurochrome for five minutes, repeated again after 24 hours. A veterinarian should be called if the infection does not clear up.
Red leg is a common disease in frogs caused by poor husbandry. It causes small ulcers, hemorrhages, and reddening of the skin around the belly and underside of the thighs. The infected frog should be kept warm (85 F) and immersed in a 2% solution of copper sulfate or potassium permanganate.
You should always consult a veterinarian if you think there is something wrong with your frog!
RECOMMENDED READING
All About Frogs, http://allaboutfrogs.org/info/species/horned.html