I've heard of it, seen it, never used it personally...
It's ammonia based, which means it "eats" chlorine, increasing chlorine demand with no sanitizing/oxidation effects since all the chlorine is used to breakdown the ammonia, then the chloramines...
In practice, all ammonia based algaecides do this, as well as increasing the opportunity for foaming, greasy films, and follow on algae blooms as people who don't understand what happens to the chlorine fail to get the chlorine levels back to an acceptable level. They add 1lb, or 1 gal, or 3 pucks, because that's what it always takes, and fail to realize how fast that chlorine is absorbed in the ammonia battle without helping the pool- then they think the chlorine is at fault!
I think chem-geek had a post about the amount of chlorine needed to get rid of ammonia- and it is large amounts!
Meaning you have to add that much chlorine, plus enough extra to sanitize/oxidize the algae in the pool!