I have a 15Gallon tank with about 10 apple snails in it. I believe the calcium levels in the tank are to low because the shells of the snails have holes. I read online that you can use anti acid tablets to raise the calcium levels in the tank because they are made of calcium carbonate. I added 2 750mg tablets to the tank. My KH plummeted to 2 degrees from around 6. I am not sure why this is happening? I thought Kh was how much calcium is in the water so why would the Kh Drop if I added more calcium?