Size of Gravel

Generally, 2 - 3mm is perfect. Anything can work, but if too small, it compacts, too large and the roots can't get a good purchase. I would be happy with anything around 1/8" or so.
 
3/8" is very big.

I have coarse sand mixed with laterite and topped with a litle gravel. It works well for the most part but I still sometimes have trouble getting plants to stay put.
 
Flourite and Onyx Sand (not gravel), seems to be just right - in my opinion...

I don't like the look of large gravel, and think it makes some tanks look smaller. Fine sand is too small for most planted aquariums.
 
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