I don't do anything special, filtration or water-change wise, for our adult Mbu in the 300G. And there are probably another 30-40 small cichlids in there with him. A 50 gallon wet/dry sump and two medium-sized canister filters. 50% water change once a month, give or take. I do use and recommend "Pothos/live plant filtration" (there is a thread about this here on the boards...) but aside from that, nothing special. Yes, big puffers poop a lot but in my experience, they are not arbitrarily any messier than any other fish of that size, i.e, Oscars, arowana, big pleco, etc. If anything, they are easier since you can scoop out there turds with a dipnet. Just like cleaning up after the dog in the yard, LOL. Anyway, point being that you do not need to spend a lot of money (or even very much money) on the filtration system. Mine wet/dry is cobbled together parts from Craigslist, mostly. Yes, do it properly but Mbu (and I assume, Fahaka..) are pretty hardy fish and not any more dependent on "extra high water quality" (however you might define that...) than any other fish I have kept.
Just my 2-cents.
Just my 2-cents.