Well..
Rays (elasmobranches) in general are pinnacle predators, that use electrosensory to constantly scavenger for food. They don't have many, if any, natural predators in the wild. Cichlids and Stingrays in the wild don't encounter each other much, and if they do, it doesn't last long.
So with that being said, the ray likely won't be smart enough to understand territory and boundary. Although they are considered to be incredibly intelligent, they are at the mercy of the cichlid's disposition.
Cichlids are also amazingly intelligent and have the ability (which is one defining characteristic of cichlids) to identify other Cichlids. They find other cichlids to be the largest threat to territory, breeding partners, and food sources. This is why you will find that a Cichlid will dominate another Cichlid, but perhaps ignore a potamotrygon, pangasius, or osteoglossum. Just keep in mind, the Cichlid has the ability to destroy with it's mouth, and depending on the species could easily kill a ray.
Roll the dice
Know your cichlids.. just use precaution. Tank Space and Fish Sizes play a huge factor..
Public aquariums/large ponds ~ Yes..
125g ~ No..
