This is how water changes may not get you to your goal unless they are quite large
Water Changes in Reef Aquaria by Randy Holmes-Farley - Reefkeeping.com
Figure 8. Nitrate concentration as a function of time when performing daily water changes equivalent to 0% (no changes), 7.5%, 15% and 30% of the total volume each month (in other words, 0%, 0.25%, 0.5% and 1% per day). In this example, nitrate is present at 0 ppm at the start, and is accumulated at a rate of 0.1 ppm per day when no water is changed.
Figure 12. Nitrate concentration as a function of time when performing daily water changes equivalent to 0% (no changes), 7.5%, 15% and 30% of the total volume each month (in other words, 0%, 0.25%, 0.5% and 1% per day). In this example, nitrate is present at 100 ppm at the start, and is accumulated at a rate of 0.1 ppm per day when no water is changed.