Flourite..?

What color is your rock, and what color is the fluorite? I put sand over my fluorite since I was sick of seeing the ugly color, and what do you know, the mts snails mixed the two together while they were burrowing/surfacing. This is just as a heads up, but I added about 1~1.5 inches of sand and now its mixed. I do have a ton of snails though...

If you still want to top it off, I would just drain as much water as you can, and then plop it in there. Just pull the plants up so that the crowns match the new substrate depth.

Be sure to wash the heck out of the fluorite because your water will be cloudy for a while if you don't. You should start a seeding sponge if you're going to replace the whole thing though.

that would be a sponge with the bacteria in your tank. What happens is all of your bacteria (or a lot of them) will colonize upon that substrate that you use. When you remove it, you risk causing the tank to recycle. So what you want to do is to run a sponge in there, or a sponge on a filter/powerhead. this gives another surface for them to grow on, so that way they can eventually move onto your new substrate without having to worry about ammonia spikes. As an other note be careful if you do some heavy duty trimming on your plants. Plants will also affect the cycle of chemicals in your tank. Once I had a plant taking over my tank, so i thought i would trim it back. Apparently I trimmed too much and apparently it caused a small spike. Just my .02