When my 300 is set up and running fine, I'm considering adding more rays in addition to the 3 that I have. Currently I have one each female and male hystrix and one male retic. I'm considering a marble or two as well, would that be ok in that tank (72x36) and with the other rays? Female or male? Would like the female/male ratio within check. Also a good spot to get the marble pups, shipped if possible.