New guy with a quick substrate question.
I have a 20 long that is currently undergoing fishless cycling. I'll be using some of the hearty, lower-light flora for a South American tank. I have 1.5-2" of t-grade color quartz in the tank and I'd like to add a plant friendly substrate.
I want to add a layer of flourite underneath the current substrate. Is it preferable to add this under, or on top of my existing substrate? Would it make more sense to just change the substrate entirely?