Hello and welcome to FF Walker! Well first thing is to read this care article: Frog Forum - Pacman and Horned Frogs - Ceratophrys - Care and Breeding . Second is not to worry much about enclosure size; frog is fine there for a bit of time. You do have to take care of a couple things. First, please let us know what is frog's length from snout to vent (SVL). Second get rid of the moss since it's an impaction hazard. When mixing the shredded coco, add dechlorinated water until it's slightly damp and clumps on fist without dripping water out.

You can use red lights, black lights (moonlights) or heat emitters. Avoid daylight type bulbs since they can hurt your frog skin and eyes. To prevent overheating tank, get a manual (rheostat) or automatic (thermostat) to control the heating bulb. Lamps dry air, so you will need to cover the top screen with glass, polycarbonate, or even Saran Wrap. What I do is cover whole screen top with Saran Wrap taped to edges then use a sharpie to mark off around light fixture. Then add 1 in. around marked circle perimeter to prevent heat from melting wrap and cut off a hole for light. Covering most of top will increase humidity and the inch perimeter will also provide ventilation for frog.

Water dish should be cleaned daily even if it looks "clean." Many frogs poop in water and you will smell it; others will poop in the hole they bury then move to another one. Sometimes it will be buried but it's easy to find because they are pretty big logs. Spot clean tank daily and replace whole substrate once a month.

Would not feed mice more than once a month. Perfect food are night crawlers and you can probably get Canadian NC at a bait shop; do make sure they are not dyed. For your frog can feed whole ones and would start dropping them in front of frog's mouth. If frogs eats it; then feed one large (4-6 in.) worm per frog in. of length. For a full grown frog (presuming yours is one at 1.5 years old), would dust food with CA/D3 2X and vitamins 1X monthly on different weeks. Can also feed Dubias or any other large roaches sold locally at pet shops. Good luck !