What can I do to make my pool clear?

[Torchwatch]

In Britain we have a blue green algae that is cyanogenic, in lakes and ponds the cyanide kills off all other wildlife, and can make humans seriously ill.
The breakdown of barley straw can kill off the blue green algae, placing the straw in a "J" cloth bag keeps the pond, lake or aquarium free of loose straw, not heard of this treatment being used in a swimming pool though.