Clearing the pool of dead algae will only occur after the shocking process is successful.
Most people have been schooled to think that throwing shock product in is the correct way to shock. If you read here you will find that this does not work, and that you have to maintain shock levels rather than raise to shock and walk away.
Read pool school (white button, upper right of this site) and especially the how to shock your pool information. If you follow the guidelines there, the filter cartridge will eventually catch the dead algae because none is growing back when chlorine levels fall below shock.
Even 1ppm below shock level for more than an hour or so can cause a stall. If you are repeatedly falling below shock, algae gets a chance to re-grow and the pool owner just ends up chasing their tail for weeks on end. Shocking properly stops tail chasing and you will see the results in a few days instead of weeks and weeks of same.
And of course, a good test kit is essential. Without it you can only guess what's going on and you won't be able to know if you fall 1ppm below shock an hour after adding chlorine. Read through all the information, and read threads where green swamps are cleared to sparkly. You will soon see that once pool owners shock properly, everything just falls into place and the pool clears right up. Even crummy Intex filters can clear a properly shocked pool.
