Instruct: Classify Amazon reviews into positive or negative sentiment
Query: works as intended

This product works well at lowering the phosphates levels in my pool, and keeping algae away. I had problems with black algae for several years, the algaecides were not getting rid of it. I found out about phosphates online, and asked the pool store to check for them. They offer free monthly water checks, but had never told me about phosphates before. I had high phosphate levels, around 500. They tried to sell me a 2 liter PhosFree for $50, but I knew of lower prices online. I bought a 3L PhosFree for $26 shipped. Used as directed, now my phosphate levels are near 0, and the black algae is gone.Just ordered my second bottle.