Here's a basic run down on the feeding process.
You're going to add protiens to the tank, including nitrogen and phosphors, in the form of food. You'll add a certain amount weekly.
The fish and bacteria will convert that to different forms of protiens, but still protiens. Phosphates and nitrates will be end form and could be measured in a weekly addition amount measured in ppm
depending on the bioload and feeding habits.
You are proposing on doing a weekly water change of 10 or 20% weekly. That means you'll remove 10 to 20 % of the weekly addition of nitrates and phosphates. Or more simply stated, you'll be leaving 80-90 % of the weekly addition of nitrates and phosphates in the tank. What is your plan for the huge amount of left over protiens you'll leave in the tank? FYI algae LOVE protiens. Cyano
If you don't do something other than water changes, your nitrate and phosphate levels would slowly increase until the 10 to 20% removed is equal to the amount added weekly and would probably be in the 80-100 pmm range. At least, that is whaty mine go to until I added a sump, skimmer and cheato ball. Now its 0.