You can use Ameca splendens as feeder fish if you have too many of them. Do not feed the big males to your big fish because the female goodeids DO NOT stored the sperm pockets like poecillids (guppies, mollies, gambusia, Xiphophorus etc) therefore they must be bred every time after had a batch of fry. Even if you removed the dominant male, another male will take its place and become the dominant male. The dominant male wont let smaller males to mate with the females. So you can feed small male goodeids to your fish but once a while you can replace the dominant male with a small male of same colony before the dominant male get too old to breed.
Now on female subject, larger females often produce bigger spawns than smaller females. Depends on the size of females and the numbers of fry, sometimes the large spawns often have small sized fry while larger spawns always produced larger fry. Most females produced a batch up to 15 to 30 fry. If you were lucky, a female might produced four batches of fry per a year. So you need to save few large females for fry producation.
I used to have Xenotoca eiseni as feeder fish in past as they are very proflic breeders but I sold them. Now I really missed this species. Someday I will try Ameca splendens out sometimes but right now I have only Goodea atripinnis, Ilydon furcidens, Characodon lateralis "Los Berros", Skiffia multipunctata and Xenotaenia resolanae.
Ameca splendens aint too hard to obtained if you look harder. Fish clubs, aquabid, private breeders and sometimes LFS always have supply of this species along with Xenotoca eiseni (redtailed goodeid) another common goodeid species. Ameca splendens have been in Aquariums for 70 years and there is a remnant population has been found in El Rincon waterpark near a town of Ameca.
