I have kept California Rays, Yellow rays and cortez ray together, the only "gray zone" was that the California and Cortez may have preferred the water temperature a little cooler, They all mixed well together. I currently have an 8 x 3 x 2 with a horn shark, two baneded bamboo (punctatum), a gray smoothhound, four small cortez and a medium (8-10" disc) california and a few mild tempered fish with no personality conflicts. I have very little decorations, just a few larger peices of live rock in the middle for caves. I have to perform weekly 1/3 water changes and rinse the prefilters about 3 time per week to keep the water right. The filtration system is a very large wet dry with a dual down draft protein skimmer with ozone injected into the skimmer.