Since I went with a dark tank (big rocks, driftwood, anchored and floating plants, black background) I went with white gravel. It actually looks pretty good IMO
Finely crushed gravel. Its the size in between regular gravel and sand.
Gives the amazon feel and at the same time prevents a certain degree of waste from sinking into the substrate.
black gravel , i like the way sand looks but i dislike the toxic gas pockets that can start to form if your not stirring it up enough, wich can be fatal to your fish.