Hi, Thanks for taking the time to rate this item. Algae is a tough task and probably will take multiple tools to conquer, including an algacide or lots of chlorine product. We recommend you run your pool filter for longer hours each day - or even 24 hours a day at first. This particular vacuum does work well on small debris and dirt from the bottom of the (gunite) pool, but as the debris is being sent right to your pool filter, it is also important to make sure your filter is clean by backwashing more frequently or taking it apart to clean the inside elements, which are likely full of algae. Assuming you have a hard surface gunite pool, in addition to the vacuum, you will need good pool brushes. For gunite pools, we recommend a Stainless Steel bristle or Stainless Steel/ Nylon combo bristle brush, especially for black algae. Of course NEVER use a stainless steel bristle on a vinyl liner pool! Hope these tips are helpful. Please don't hesitate to contact our Customer Service Dept. at 800-854-1492, Monday-Friday, 8:00 am-4:30 pm Pacific Time or e-mail us at info@poolmaster.com with further comments or questions! Sincerely, Poolmaster, Inc.