A lot of the larger canister pond filters require external pumps, unlike some of the larger aquarium canisters. If you don't mind a big pump with tubing in the bottom of your tank I guess you could use them.
Plus a lot of the pond canisters don't have shutoff valves, when it times for service thats OK outside, but not under your aquarium.
If you go even larger like the Aqua Ultra Violet Ultima II filters, then you need larger more exspensive external pumps, then you need to have the waste port plumed somewhere and it just gets more involved.
I would only use pond filters on very large heavy stocked setups.
