If I remember it takes a while before they reach the 2" mark. Maybe a couple of months 7-8. I think, don't quote me on this. I would start the con tank first and grow them out then get the fish you want to feed them to. I did this years ago to feed my jacks and jags. My friend told me to set up 2 tanks 1 for the breeding pairs and the other for the grow out tank. So I had like 4 tanks going at one time. Kinda lost interest in using my money to feed the cons just to feed to other fish so I just focused on cons. I actually made more money raising cons then growing jacks and jags. Ended up with more than 20 generations of cons before I stopped for 2 years. It all started with 4 pairs