Correct me if I am wrong, but I think that Cartman's question was what normally lowers the ca level in tanks. Certain corals use dissolved calcium in the water for life. Over time they will lower the level of calcium. Calcium is just like any other water solution, it can only hold so much. Once the level of calcium is too high to be dissolved it precipitates and then starts your problems. If you are going to use any calcium additive then get yourself a test kit and know the acceptable levels. But I am no expert, just going on what I have learned in chemistry and my own aquaria experience. Hopefully this was what you were looking for Cartman. Looking forward to seeing the shart at Bass Pro. I live not too far from there.