Canister Filter as sump?

[reef-junkie]

I am currently in the process of setting up a 40 gallon frag tank.
I want the tank to be completely clean (no rock and no sand)
so obviously I'll need to have a sump. what I was wondering is instead of setting up an overflow and return, could I just use a fluval fx5 canister filter, remove all media and pack it full of live rock rubble? I plan on going skimmerless as I will have no fish.

Has anyone ever done anything like this or have any insight as to whether this will succeed or fail?

Already have the canister filter on hand