I use much deeper caps in my tanks. In my first dirted I used a layer of gravel to cover the bottom, potting soil to cover that, followed by an inch cap of sand and all sorts of wood chips and gunk have surfaced with zero digging or replanting.
In a later tank, gravel, dirt, gravel 2 - 3 inches of blasting sand and I have a digging banjo cat in that tanks with no problems...
If you have healthy roots/plants, methane rapidly oxidized.
Buy your sand at menards or tractor supply.. pfft on pet store sand prices.