Hello and welcome to FF! I would also get an established 1.5 to 2 in. baby/juvie like Lija stated. Get it tong trained and feed it not dyed night crawlers from Walmart or a local bait shop and it will grow very fast. Cut the worms from pointy end, mouth size for babies, body length for 2-3 in. juvies, and give whole worms to larger frogs. Lot's of good info on their care in this article: Frog Forum - Pacman and Horned Frogs - Ceratophrys - Care and Breeding. Good luck !