Green Hair Problem After Using Bioguard Smart Shock

[PoolDoc]

Also, does HEDP add phosphates to the pool, and can this grow algae?

Phosphonates like HEDP eventually break down into phosphates -- which is why we recommend AGAINST using HEDP unless you have a specific need to do so. But, phosphates don't grow algae, any more than carbon dioxide "grows" algae or any other plants. Both phosphates and carbon dioxide are necessary for plant growth, including algal growth. But, just as ALL pools have carbon dioxide, but not all pools have algae, so not all pools with phosphates have algae!