I had an 8" one reach 16" in just over a year then sold it before moving, it loved earthworms but also ate any meaty food like raw shrimp meat and clam bits as well as small fish.
K.O.D said:When we got ours they would only eat bloodworm, but at 24" bloodworm is not an option, we starved them and now they eat prawns ( whole ) and earthworms
here is a pic of them with the rays, they will dive under the rays skirt to get prawns!!!
Steve