What do you know, Im a king keeper and I just bought a pair of northern pines! How big are they? I purchased my pair for 175 shipped, and they are a year old and about 30 inches. 300 would be good if they were ready to breed adults, but not for young ones, maybe if they are albino (even then Id say its a little much).
Care is different than a king Im learning. They like it cooler than kings, 80 by day 70 by night. Mine have also had trouble shedding, which I hear is common with this species. I have had recommendations to place a damp cloth in the hide box while in blue or place the snake in a wet pillow case to aid in shedding. Also, since they are in cooler temps, you cant give them the enormous prey that you can a king. They take smaller prey more often better than they do large prey. I dont have it all figured out yet, as I said I just got mine, so good luck!