ThePBM;1013783; said:that looks like a pretty thick layer of gravel
I would say that the gravel is about 1-2 inches think on different areas. I can't quite say an accurate number because the gravel is never flat. I think its not enough because based on the rule of thumb that I have researched, its supposed to be 1 pound of gravel/substrate for each gallon of water. Of course that can also be just a speculation based on experience and what looks good on the tank. My tank currently have 40 pounds of gravel which is 4x10lb packs of Art Rock smaller/smoother gravel.