Don't move up if you want to feed Bio-Gold+ ... it comes in only mini and medium. It is harder to get them back to smaller pellets than moving up.
It has much higher vitamin content, and is cheaper online than the store price of gold ... but double the price of gold on the shelf.
I am feeding a bit of both, but after a few medium pellets, he wants the bigger ones. I only have a few bigger ones left, but just testing the waters.
A greedy O will eat whatever, but after a few bites, mine seems to remember how to be finicky again.