i know a guy who has a 125g reef tank, then a refugium, a sump, a frag tank, and a calcium reactor. i have yet to see a better looking reef tank than his.
all of that is 400 something gallons total water connected, and he only does 10% water changes every 4 months.
again, this was one of the tanks in the local reef club's little "tour of tanks", his was last, and it was for a good reason, because it made all the others look pretty sad... lol