In a month we got a 7inch bamboo to get 11 inches, feeding twice a day. I am sure the marble isn't as much, but he would get to a certain size then start to grow a lot slower. So depends on the size of him too...
The Marbled Catshark - is in the same genus as the Coral Catshark, and it is from Northern Australia. So it is definitely a tropical species just like the Coral Catshark is.