I've had a 10 gallon aquarium running for about two months now with flourite black sand as the substrate. It is 1.5 inches deep in the front and 3 in the back. Ammonia-0, NO2-0, NO3-about 10, Gh-about 11, Kh- about 11. It has two plain old 15w flourescent fixtures over it and I dose using the pps pro system along with excel. When I was doing maintanence I pulled up one of my crypts, and a ton of bubbles came out of the sand. Same thing happened when I pulled up some other plants. Is this normal, or should I be worried? Also I read somewhere that flourite black sand doesn't do any more than regular sand does for the plants, is this true? Oh, by the way, I do 50% water changes every weekend and the stocking is: 6 amano shrimp, about 40 red cherry shrimp, and 6 Heterandria Formosa.