I have a 25 gallon tank that has regular gravel from petsmart that is just rocks. I was wondering how much of a difference i would see in my plants and aquarium as a whole if i switched out this gravel for the eco-complete. I used this substrate calculator (http://www.plantedtank.net/substratecalculator.html), and it said I need 40 lbs to cover my 25 gallon with 2 inches of substrate. Is this a good calculator? And is 2 inches a very good amount of substrate for plants?