Thanks! Far from it. There are certain types of cichlids that form symbiotic relationships with rays. Eartheaters sift through substrate to find food, following a ray that is constantly kicking up substrate is a food source so they follow the rays in the wild. Search for "nuclear followers association" and you will see what I am referring to. The key is not getting an eartheater that is too small or it's easy prey for rays.
Fascinating, I just read up on it. The article I saw on practical fish keeping said that some cichla and crenicichla species will do the same thing. I am inspired by this set up, I would love to have a tank of rays and eartheaters, what a diverse mix!