I bought four platies at one point and had over 30 in my tank in 2 months.
Once my Oscar was introduced to the tank they had all "disappeared" in 1 week.
I'd have to go with guppies to be honest as they are unbelievably prolific, producing broods of 50+ every 2-3 weeks! Are you hoping to breed the feeders in a seperate tank or in the same tank as the bigger fish?