All gravel in one, Sand in another, 80% plant substrate (aquariumplants.com brand)/20% gravel and combination in the last (substrate/gravel/peat moss).
I have to agree with M. here, plant substrate is not anything like gravel. Most planted tank substrates are not "like" or "similar to" gravel. They're a category of their own.
K. Blane
I didn't vote, because I feel like I'd have to check most of the boxes and a couple that weren't there . . . :idea: