Hey kreker. Welcome to Aquarium Advice.
I would go with a sump, for more than one reason. It adds more water flow to your tank. Gives you a place to put any unwanted live rock hitchhikers, if you do get any. It gives you a place to put your heater and skimmer, so it doesn't clutter up your tank. And it adds extra water volume, which means more control over salinity. Canisters are good too, if you like, but alot of people either fill them with just rubble or carbon, and use it for extra water flow. Of course, everyone's opinion varies, and this is just mine. I wish I had the room for a sump, but don't.
The canister will maintain aerobic bacteria. The main problem is, like you said, lack of maintenence in all parts, leading to usually excessively high nitrates.
, and don't forget the pictures.
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