That's fine on the pictures.. if you can get anything, it might be helpful
If it's hard to do 2 water changes a week, you may be able to get away with a 100% every 4-5 days instead. Bettas themselves don't cause a whole lot of bio load, but as long as there isn't food left over then you could most likely get away with the 4-5 days rather then 2 per week.
We always recommend a certain number/times, but it's just a recommendation. Yet sometimes you find something that works best for you and your time/fish. I personally do mine 100% every 4-5 days for my 1-2 gals unfiltered :) it works great for them and me.