I have often had my tanks overplanted, to the point that little light was able to get to the bottom of the tank. SOme plants will have rotting leaves near the bottom if no light, or not enough light, can get to them.
Also, fish do like to move around. One good thing about an overplanted tank is that you can sell or give away plants. If your tank is overplanted, I am sure that there are a lot of ppl on here that would likt to PM you about plants.