I use a .5mm particle with an analysis of 52% protein. My newly hatched koi love it and it sure saves me time grinding and hatching live food. I actually use this ground into a fine powder that mimics a cloud of plankton for a week, then I switch to the .5mm food that is not cloudy. It would be perfect for some of you who hatch many fry. It is fish meal-based and I sell both types it in smaller bags.
J & J Aquafarms
John