I would do multiple forms of filtration with the main system being a wet/dry or sump type system. That really is the best, most effective, low-maintenance form of filtration you can buy... Set it up correctly in the beginning, and you will be rewarded in the long run with great biological filtration. In addition, I would have some powerheads running to hit any dead spots so no area goes unfiltered. You are gonna have four big slobs of fish, there, so a canister filter is not the best choice as you will be cleaning that thing every week. Not to say that is not good for extra filtration with different media, and water polishing. But seriously consider a wet/dry or a sump working off an overflow.