Originally Posted by SmokeNLark
Kytkattin, 10% is not nearly enough once or twice a week, planted or not. A bigger filter helps, but when the waste gets down to nitrates, it still builds up and no filter can get rid of that. Thus, water changes still need to be sufficient. Please consider upping that. Especially since it's divided. I would probably be doing 30-50% changes twice a week on that. Or like 80% once a week.
If your tank is planted with the right kinds of plants, I know some people skip doing water changes and just top-up the water when it gets too low. NPTs work on this theory.
My sorority tank was never cycled, and has 7 females in a 10 gallon tank. Yet because it was heavily planted with stems and floaters, I never saw an ammonia reading, and my nitrates are essentially 0-5ppm. That gets two 10% water changes a week and topped up with whatever water I have left over.
My goldfish tank has been running for 3 years now. It is fully cycled and is basically what I use to jump-start new tank cycles. Unless your filter media is literally falling to pieces, there's no need to completely restart a tank. By removing that much media and rinsing out the substrate, you would really be risking a mini-cycle.
I own several sensitive species of wild bettas and natives, and I wouldn't want to so drastically alter their environment like that.
Personally, I don't go by books or what I read online. I go by how they are behaving, but also what my test kits tell me. Every tank is different, and there's no hard or fast rules about maintaining them.