What is better to feed my turtles?

I'm going to petsmart today (the closest petstore that actually takes care of their fish is 45 minutes away) and idk what type of fish to buy for my red eared sliders. I usually got feeder goldfish that the petstore bred so i knew they were disease free but now im at petsmart, the feeders there have a high risk of carrying disease. I was planning on getting either Rosy Red Minnows (The tanks are crowded but they all seem active). Comet goldfish (Very crowded tanks but seem somewhat active). Or guppies (Not in crowded tanks, active, but expensive). If i got the guppies, i was planning on breeding them so i can use them as feeders because guppies look to cool to use as feeders. Also, what fish can I use to cycle my outdoor pond? I'm making a 150 gallon stock tank pond for my 2 RES (they are currently in a 55 gallon). Remember, these fish are in an outdoor pond and they can't be expensive because they're probably going to be eaten anyways. I don't wanna put those feeder minnows and goldfish (disease probable).