I have moved a number of cichlids to my outdoor ponds in Wisconsin for years.
Some were able to take the wide fluctuation in temp, some were not.
I found species from sub-tropical areas like Uruguay or northern Mexico did well, species from northern South America or countries like Nicaragua or Panama did not.
I used high altitude mexican live bearers like Xenatoca as ditherers, and fry producers because they they could also take the cooler, and erratic temps. And there were always tons of dragonfly nymphs and other aquatic insect larvae to supplement the cichlids diet . Cichlids like Gymnogeophagus, Australoheros, Uruguayan Crenicichla, northern Herichthys types, and some Tilapines did well.
July cool spells killed pearsei Parachromis and other cichlids that come from more stable environments.
Until I gave my ponds steep sides that dropped over 2ft deep, my most common predator problem was with raccoons, with shallow sides of 1 foot or so, they could easily wade in, catch sleeping cichlids at night, and they would eat the heads, leaving headless bodies on my patio.