Keeping your swimming pool water clear is no longer a matter of trial and error and daily experimentation with different chemicals. The effectiveness of ALGI BLOC is 100% guaranteed and it’s long lasting.Since ALGI BLOC kills the algae, you only need to use chlorine before swimming to kill any bacteria. And as you only need to use ALGI BLOC twice a year, imagine how much you will save on the total cost of chemicals for pool cleaning!