The chances that these blues you saw were just regular channel catfish. I has yet heard of a true blue catfish being sold in aquarium trade. Not mentioned that these blue catfish are not good aquaculture fish.My LFS had them once, but i was unable to buy at the time. They were blues, I checked them over real good. And if you keep the temperatures right and don't over feed, they grow at a regular rate, not over the top like when they are wrongly put in a tropical tank. but they do grow slower than channels already. Good luck with your fish!