Crushed walnut shell substrate for baby ball python?

I just got a baby ball python today, and got some crushed walnut shell substrate for her 30g tank. I also bought a zoo-med brand under the tank heater. I just read on the insert and it said not to use it with crushed walnut shell substrate! Can i still use it or what would happen? It's one for a 10-20g aquarium, she has a 30g. If it really is dangerous to use, what should i do? I cant buy anything new for her tonight as the pet stores are closed now.