Hi,
Not sure why you're having such an aversion to adding ferts. This is like saying you want to avoid feed your pets. If you want to avoid adding ferts entirely then you should probably think about deleting the CO2 because increased CO2 causes an increase in the demand for ferts. I suppose if you have a high fish loading and if you feed frequently though you could get away with it.

Since the pricing is similar you might do better with Aquasoil in lieu of Flourite due to AS higher nutrient content.

Remember to save some of your filter mulm and some of the gunk now lying at the bottom of the tank and mix that in with the new substrate. This adds bacteria and organic matter to the sediment to help establish the bacteria development in the new substrate. Also save some of this mulm to seed the new filter.

Cheers,