Chocolates are another species I had considered.Severum, festivum and chocolates for SA cichlids. I had a Geo Tapajos that ended up chow when I was gone for a few days, constantly being right on the sandbed made him a prime target. A larger specimens would have worked better/longer. My cichlids eat a lot of food before it gets to the rays, something to consider when you want to get the ray on other food.
My ray is eating prawns, bloodworms and earthworms. She is 3 years old and the previous keeper said she is very laid back and has not eaten fish as small as a zebra danio.
Having said that, I don't want to take any chances. I would love a shoal of silver dollars but also a cichlid or catfish that would eat any bits left between rocks or branches.