Canister filters will work on a reef set-up, the key is to change and clean micron filters weekly, and pwc
's, as above mentioned.
Is it as good as a sump... No. But it will work.
I ran a 135 tall mixed reef, on 2 Magnum 350's and a hang on skimmer, for over 6 years. With good supplemental circulation, in tank, and above maintainence.
Was it the way I wanted to go?.... No
Was it a hassle?.... Yes, but it did work
I feel removal of any large particles, with some mechanical filtration, is always advantageous.
This is that same tank 1 1/12 years after 180 upgrade... Almost 8 years and counting!!
Ps. I had 12 fish( 2 being 5" tangs) and most of the coral in 135