I am starting a 20l low tech planted tank and I am really torn on substrates. I have a 10 gallon with eco complete that I really don't love look of (don't hate it either, it just looks okay). I also have a 7.5 tank with PFS which looks very natural but shows everything.
Both grow plants like crazy with nothing more than flourish occasional. I stir the sand every 2 weeks and most of my plants have grown great from bulbs.
I am considering flourite dark, or flourite black sand for my 20l or plain natural gravel mixed with floramax (I like the darker look with the floramax).
I can't choose and mostly because nobody near me has any flourite dark out to see. It all looks very light in the bag. I was looking for a deeper brown color.