I think it may be possible that Addy has a different species in Arizona than the ones we have here, I've never seen them balance out, One primary reason I rebuilt my pond last year was because of mosquito fish, here are some things I tried to do in order to get them eliminated or at least reduced and controlled, I added a channel catfish, LOL, Not a good idea, by the time he started eating mosquito fish he had already eaten all the baby goldfish first, tried putting a oscar in the pond, he helped for a while but when it started getting cold I had to bring him inside, mosquito fish breed when it's warm or cold, they don't care. I tried emptying the pond, Moved all of my goldfish and koi to a large holding tank, emptied the pond and removed all the gunk and stuff from the bottom, thought I had them all. refilled the pond and I guess some were in the bog, They restarted again, by the end of that season I was removing literally thousands out a week, . Then the rebuild last year, This time I took the good fish to my dealer to hold along with all my plants, About three days before I pulled the liner, I added a gallon on clorox and poisoned the whole pond! Pulled the liner re-dug out installed the new skimmer and pumps, new liner, the whole deal, Cycled the pond and all looked good, went and got my fish and plants. SOB I didn't clean the plants and brought them in again! This time before they started breeding I guess I was able to get the two that made it in with the plants. Best thing to do is net as many out as possible and try and keep the #'s as low as possible. If you got the #'s low enough a predator fish may help but you have to be sure that your koi and goldfish are way to big to eat or they will get them too. Considering where you live, A Texas cichlid may work, I would only get one though and watch carefully, they get mean but may leave bigger fish alone. I seriously doubt a grown Texas cichlid would bother a 16" or larger Koi, as for goldfish, I wouldn't be surprised if a texas cichlid would try and eat fish almost the same size as itself. Good luck!!!!