Canister Filter as sump?
 

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

have seen some posts were a canister is used but usually on a nano (and no skimmer)

Hi
I ran a big Aquanova2000 lph very successfully on a 50 gallon tank which is about the same size as your FX5, I think the FX5 has even more flow than the filter I used so it should work very well for you for a frag tank.

Did you use live rock inside your filter? Almost as if we'd be treating the canister as a sump itself.

I ran an FX5 on a fish only tank with all media, sponges etc removed and filled with live rock rubble. But it is no substitute for a sump. No experience using on a frag tank. If you plan on growing frags you would want excellent water parameters and IMO you won't get that with a canister filter

Canister
 

Depending on what it gonna put in there. If u doing softies and zoas and polyps etc this will work good, if u want it all sps frags +1 to madreefer it's probably not the best

canister
 

So long term I'd probably be better off just setting up a sump.
At first I plan on only having zoas and some acans / brains but down the road I definitely plan on fragging sps.

Yes I did, filled all the media trays with live rock rubble and it worked great as a sealed sump so to speak. The FX 5 should give you tons of flow as well.
I only had lps softies & zoes so I can't comment on how it would work with sps coral though.

I'm wondering how well I would fair if I didn't overload on sps frags.
approx how many lbs of lr would you say you were able to fit into the canister?

Im new on this hobby but i been running my tank with a canister and till this point no problems at all my tank is small 30 gl, 55 lb of LV 40 lb of aragonite sand mix soft reef and fish.- my filter is a fluval 305 with sponges and 3 lb of LR crumbles
and 2 bag with aragonite sand and little chunks of LR, seriously i been hearing a lot of bad things about canister that i get confused but i experience person in this hobby give this idea with the canister and he said just follow your heart :)