Thanks guys! I agree with badflash here. I have seen this in every species that I have successfully bred. You may think you are the odd man out when you visit a hatchery, and see all the tanks of nearly identical sized fish, but a lot of time has been put into sorting these fish. In fact I am certain that If I were real production oriented, I would take the time to sort them so that each size class could be fed for optimal growth. There are many reasons for the size differential, but I think that the primary difference is aggression. I notice that many fish rise to the top and come half out of the water at feeding time, and others mill around below taking the crumbs that drop through. As soon as the feed at the top is eaten the more aggressive fish drop down, and start eating the crumbs as well. These are typically your larger fish. Though not always.