Hello people, this is my first time posting in this group...

I work at a local pet shop, helping to manage the fish room, One of
my coworkers recently gave me a 50 gallon D.A.S. tank, which I plan on
planting heavily, installing a CO2 system... the whole nine yards.

My question concerns gravel. I want to use Seachem Onyx Gravel,
Seachem Flourite, and Crushed Lava rock in a ratio of 2.3.1
respectively... Have any of you ever tried anything similar to this?
Does this sound like a sufficient substrate for the plants? Has
anyone ever had any issues with these products? Any advice you could
offer would be appreciated.