I've done it as soon as 3 or 4 weeks like Jim. I've also been short one system because of tank failure (i shut the tank down because of bad seams) and had to keep them in cribs for 6-8 months until I could expand. I used large cribs and split the pups in pairs but was a life saver in emergency.For how long do you guys keep the pups in these cribs before moving them to a grow out tank?