Too Much Terrarium

[Rene]

About a month ago i had a friend give me 40 gallon breeder tank. I was thinking this would be a great Terrarium set up for a scorpion. So i went ahead and purchased everything. Substrate to fill the tank 3 inches deep, temp humidity gauge, heat pad and lamp. So Yesterday i purchased an ASF at the local pet smart. I was given the only o e they had a small young male. I carefully removed him from the plastic bin they gave me and placed him in the tank. And he quicky went to borrow under a log. Now im thinking is this setup way to big for a small scorpion. Should i take him out and place him in the petsmart bin till he gets bigger? And what wattage build can use to properly heat one side of the tank? The setup i have now is at 70 degrees with 70 humidity