feed them hard boiled egg yolk. Do water changes every day and continue removing the dominant fry. Let the dominant fry dominate until you have some big ones and some small ones. Then select the big fry out and repeat until every fish has had a chance to be the dominant fish. These will always grow faster. in nature the big ones get bigger and pick on the little ones until the little ones get smaller. to get all the best bold fish you can select this way until you have one fish to a tank. if you have enough tanks you can end up with quite a large number of high quality fish from one spawning