The number 1 feed that I've seen recommended is the Mazuri brand. Now, there are 2 types, one is flock raiser and the other one is.... I forgot. Mazuri is a Purina brand, and I would think its carried by the TS. Its kind of expensive I think. Also, your local feed stores can order it if they dont carry it.
I went to local feed store & asked about Mazuri.They didnt have it but would order it & it would take about a week for the shipment to arrive. They did have another type of food that they carried that was for waterfowl (and MUCH cheaper). The protein level they said was 16% so I went with that. I would def call local feed stores first to see if they have feed for waterfowl..
Protein level was a big concern for me because I nervous about my guys developing angel wing. I've read its not that hard to correct, but being a newbie, I was intimidated by it. I made sure my geese spent time outside everyday so they could run around & splurge on grass.