Caribsea Tahitian moon sand is inert where Flourite black is porous clay which has the ability to hold nutrient's for a long,long,time.
For planted tank,I would choose the fluorite black to help supply root's with nutrient's it adsorbs over time .
Need to rinse both ,and best way I have found to rinse large amount's quickly, is to place some in an old pillow case and run garden hose into the pillow case till water run's clearer than at first.
Then dump the pillow case into small tub and repeat until it's all been rinsed.
Place it in the tank and place a dinner plate or bowl on the substrate and fill the tank slowly by running the hose into the plate/bowl.
Let the tank settle for an hour, after it's filled,and then turn the filter's on.
As for black sand or fluorite dark,either or as per your preference.
Read up on em.
