I am going out on a limb and guessing this is the same snake that is bitey and defensive with you? Has this snake eaten since he has been with you? Also, a T10 is enormous for a snake that young.. You said he was hatched 8.24.19 correct? Even a 20L is really big for a new snake like that.. Understand that if you got him from a breeder which I am assuming you did, he was more than likely in a 6qish tub... You have changed that dramatically.. Probably one of the main reasons he is a little defensive.. He went from a rack and tub to a wide open fish tank.. I would NOT recommend anything close to a t10 for a long while.. I would make sure that the 20L isn't too big and he eats and adapts for you..

Good Luck..