It is very common that people don't have a problem with baquacil for the first three years. The fourth year, the water doesn't seem to clear. I read somewhere that the best way to keep a baqucil pool was the change the sand in the filter every year, and change out the water by partly draining and refilling a couple of times. So if you want to keep the baquacil, you may want to try both of these methods.