Have you thought about mixing the 500 and 600 together, that is what I have done, along with 400 as well but I doubt I will do that again, I just bought a bag of the to get my Tilapia going last year.
What you are doing is working though so may not want to change, but the larger fish may enjoy the larger pellets.
Let us know what you do.
Also how much do you feed per day, and about how many fish would you think are eating the food.
