On the average tank, stocked properly, yes, 20-25% is what is usually required. Filters remove some debris, and change ammonia to nitrite, then nitrite to nitrate. The only practical way to remove nitrate is through water changes.
Think of it like your car, it has an oil filter, but you still have to do oil changes. The filter can only do so much.
Don't do a big change now, 10% daily for a week, then do the weekly changes. Water that hasn't been changed for quite a while is probably a different ph than your tap water. Ph swings are bad for fish.
Tolak