What are the dimensions of this tank?
If I were you, I'd keep the fluorite for a tank where you can use just fluorite, mixing it up is a real pain. Instead see if something like mineralised top soil would be viable for you. Cheap but it takes a fair bit of time. Just make sure you cap it properly too. Might wanna check SOG for tubes, they usually stock a decent range.
What are your goals with this tank?