whoa whoa whoa take a chill pill man....
I believe youre tank is 30 inches deep, not 30 inches wide. It doesnt look like its 30 inches wide...
Nobody saying you need a MASSIVE tank, just enough to give the ray some room. Length wise, your tank is fine. Once the ray gets bigger though, it wont even have enough room to turn around.
And for your information, I dont own a ray now, as I'm in the process of constructed my new home, but from the years 1999 to 2005 I kept 3 motoros and 2 "teacups" (hystrix) in a 400 gallon pond. The hystrics grew to have a 9 inch diameter disc.
I believe this thread should be closed, as its impossible to get at this guy.