How soon do you have to switch a ball python over to larger prey once they reach a certain weight? Oliver, my male fader pastel weighed 394 grams when I bought him and I've been feeding him frozen thawed weaned rats. He now weighs 561 grams and from what I've seen on feeding charts, it seems like he should now be eating small rats. Is it okay to keep feeding him the weaned rats until I've used up what I have left ( about enough for a another 2 months or so) and then switch him to the small rats or is it better to just switch him over now?