I would wait until you have the 150 fish in the 310 so you can give the rays time to eat alone, or you could use a smaller tank if you go for pups. Hard water will make CB pups more attractive if you don't wanna get on your RO game. If you start with small rays you might find it easier to get the hardware in the sump and then add media down the line. Pups don't really produce too much waste, tiny mouths and tiny bellies pretty much grow exponentially though, so 6 months down the line you will want to add more media. I wouldn't touch cichla until rays are older, rays can be outcompeted pretty easily and cichla can eat themselves to death. I agree cichla are awesome though, I always look at them and feel like my 30 width won't keep them happy for too long.
