I usually do 10-20 gallons on my 180 every day. (sometimes I do it in the morning and night, only on weekends). My 55 gallons I do around 10-15 gallon of water change every other day.
Im talking about a reverse osmosis deionizing filter its not filtering the water in your tank its changing it out. Constantly. The water in my tank changes every 2 days.
Heres a link to a site that explains what im talking about