I've just literally finished a ~33% water change in my main tank Twinklecaz, a Rio 240, think it was ~6 3.5 gallon buckets siphoned off with a gravel filter and replaced in the space of ~40 minutes tops. Doing ~50% (6 gallon) water changes in my qurarantine tank every day but one for the last 8 days takes 5-10 minutes. The stats were fine in the Rio (borderline nitrite in QT 0.1 to 0.3 mg/l), but my fish (especially my pearl danios in Rio and Garras in QT) will show their appreciation with gorgeous colours and activity in response to the fresh water!