When I was Setting up my 180 I bought a bunch of sand from a guy who had sting ray tank! Thing was like 500 gallons and not much rock. It had sprig a leak and had to tear down, I wasn't able to see it running but he showed me pics of it. Can't remember his name but the Rays would eat from his hand like down town and made a nice water mess in his fish basement. Do it mermaid be the first in the club!! Would be cool for sure!!