searches

It sounds like gar like Asian carp, which would include goldfish. For some areas, maybe gar would work:

https://www.canr.msu.edu/news/asian_carp_being_eaten_by_native_fish_new_studies_find

Small Asian carp were extremely abundant following a large spawning event in the summer of 2014. When any food source is abundant we expect that predators will take advantage, but some predators were actually going out of their way to select Asian carp. Gar were particularly fond of Asian carp, which accounted for half of all fish found in gar stomachs.

It sounds like the limiting factor is mostly that once a carp gets big enough, some fish can't eat it, but some types of gar apparently get really big.

https://en.wikipedia.org/wiki/Gar

Recreational fishing of the alligator gar became popular due to its massive size and its meat is sold for food.[41] Over five decades of overfishing have brought it close to extinction,[39][40] and man-made dams have contributed to this loss by restricting the gar's access to the flood plain areas in which it spawns.[41] Some U.S. states have enacted laws to combat overfishing, and reintroduction programs are being carried out in some states, such as Illinois, where human activity has extirpated the gar.[39][40] Before being released, each gar must meet a length requirement to ensure that it has the best chance of survival in the wild.[42] Some states, such as Texas, restrict the number of gar that may be caught in a day, the season in which they may be caught, and the equipment anglers may use to catch them. Some states also impose a minimum length requirement to prevent gar from being caught at too early an age.[43] Scientists have found that the alligator gar can help maintain ecosystem balance by eating invasive species such as the Asian carp, and their success in a particular area can show scientists that area may also make a suitable habitat for other migratory species.[44]