Pretty much any feed and seed store or FRM dealer will have food in 40 or 50 pound bags. I’d go with the floating food, and it will help you keep track of the fish activity when they feed on top of the water.

Get a game fish chow, rather than a catfish food.

The fish that get accustomed to that feeder will come to it when they hear the feed hiting the water, after a few feedings it wont be floating away.

They turtle are just something ou’ll have to deal with.

hope this helps

Catfish food from an ag. feed store?
That probably sinks. If it floated, it would wind up around the edges of the water.