[header] How to control an algae bloom [title] Perform a partial water change in your tank. [step] Partial water changes are one of the most efficient ways of combating algal blooms in your tank. By removing a portion of the water and replacing it with algae-free water, you'll essentially dilute the algae content of the water. 
You should generally do a partial water change every two weeks to protect the water quality in your tank. [substeps] Drain or siphon off about 25% of the water in your tank.