Adding plants to my aquarium with epoxy gravel?

I have a 29 gal aquarium. I would like to purchase a co2 injector and add some plants. My main purpose is to lower my pH (currently it is 8.4 with a Kh of 300+!) and to add interest to my aquarium. Currently I have 2 neon blue Gourami's, 6 bloodfin tetra, 1 spotted catfish and one striped rafael catfish. I want to lower the ph so I can have angelfish as well. Yes, I know the tetra may get eaten, but I want to give them plenty of hiding places before adding the angel fish. Currently I have epoxy coated rock at the bottom of my tank. I have read this is not a suitable substrate for aquarium plants. So how do I change the substrate on the aquarium without stressing the fish I own? Can I layer over the rock?