I would start by feeding him a weaned rat ever 5-7 days until he fills out more. Try frozen thawed first. If he won't take it place it in his tub cover it and let him alone for awhile and he may eat it. If he won't take the frozen thawed than he was likely live fed which means he will need to be fed live rats of the appropriate size(approx the same size as the widest part of the snake. Once he/she has gained to the appropriate weight feeding every 7 days will be fine. I feed my girl one frozen thawed rat every 7 days and the vet said she is ideal.