I'm not surprised that Buckman says it's good for mustard algae--I frequently buy "Mustard Algaecide" because it's just Polyquat.

You CAN safely "overdose" your pool on Polyquat, dumping in a full quart or even two. What will happen is within 48 hours your chlorine level will drop to ZERO! Don't worry, that's normal. Just add bleach/LC to get it back to the shock level and let it come down gradually.

The algae won't start growing when you this and FC plunges--I guess the Polyquat does its job! But you MUST re-shock the pool to kill other stuff. An added bonus is that Poly is also an excellent flocculant so it will cause smaller particles to clump and be captured by the filter.

Remember: The BIGGEST problem with algae is that it consumes your chlorine, leaving you no protection against bacteria and other nasty stuff. Yeah, it's ugly and gross, but that's not the issue. It drains the ability to keep the water sanitary.

It's very important to remember this difference, especially if you are using one of the alternative systems like Nature2 that claims to reduce chlorine usage. THEY ONLY ACT AS ALGAECIDES! You still need chlorine for sanitation.