Heat rocks are supposed to very bad for reptiles, and lizards asort. The heat can sometimes burn the gecko, dragon, ect ect because they are cold blooded they dont actually know when warm is HOT. As for the corn cob it shouldnt be to bad, most of the time I use a mulch for the bottom of my terrarium, its not harmful, but that is totally up to you. I know my friend uses a walnut shell sand stuff for his terrarium, another of my friend actually planted grass in his, I use mulch. Good luck. Also most pet stores if you take the gecko in they will know which one it is and they usually have care sheets and can answer most questions. If you still need answers call your local reptile vet. I know here in Edmonton there are very few reptile vets so if you live in a small town chances are you will be calling the city for a vet. Hope that helps alittle. Good luck.