2 issues- Algae and Dying torch

[reefwars]

Originally Posted by Reef Pilot

Well, you get a much higher turnover of water and export of nutrients by changing 16% of water every 3 weeks, instead of that same amount doing 1.75 gallons every day. Plus creating a lot of work for yourself. Ideally, should change about 20% every 2 weeks.

i dont understand or my math is wrong but ....... ....how does removing 16% every three weeks better than removing the same amount rationed daily?