There are only a certain number of species to choose from if you are looking at a new forage species to propagate in the pond. You don't have to stick with just one species in this pond. It is large enough to establish and propagate several... Only small numbers of each species need to be stocked, allowed to spawn and then harvested out for transfer to your fishing ponds. Some species to consider for this pond:

Lake chubsucker
Golden shiner
Red shiner
Mimic shiner
Weed shiner
Taillight shiner
Inland Silverside
Blackstripe topminnow
Bullhead minnow
Fathead minnow

All these species are adapted to life in ponds and lakes. They will successfully reproduce in them... Some better than others though. Some species may be available commercially, others would have to be collected from the wild in small numbers and then propagated in your forage pond. A year or two of them reproducing without predation in your forage pond and you'd have 100's of pounds to stock in other lakes and ponds... Obviously, there are other forage species, to include shads, sunfish, tilapias, etc, but this selection is straight up forage and nothing but forage in use. My opinion of top species to acquire and propagate would be in order:

Lake chubsucker(can reach larger sizes, in excess of a foot, allowing some adults to grow big enough to avoid predation and continue a self reproducing population)
Inland silverside(excellent addition for crappie and HSB ponds or lakes, similar to TFS in temp requirements)
Blackstripe topminnow(loves weed choked shallow areas when in ponds with predators)
Weed shiner and Mimic shiner(similar in appearance and behavior to GSH but doesn't get overgrown)

Stocking those four species and then using seines and traps, one can collect good numbers to transfer to other ponds even in a deep steep sided pond.