Lawrosa:

Didn't you say you are in NJ? If so, find a nearby Branch Brook Pools and buy their Mustard Algae remover--you'll see it's 60% PolyQuat and costs about $20, rather than $24.

I can't really help you with the HEDP, I've never worked with it as my pool doesn't have a metal problem.

Carl

PS: Ben posted this link for one brand:
http://www.horizonpoolsupply.com/sto...ategoryID=4339
C