[header] How to clean algae [title] Scrub down the side of the tank with an algae scrubber. [step] Remove your fish from the tank before scrubbing down the sides with an algae scrubber. You can buy an algae scrubber online or at a local pet store. 
You should use this to remove algae from a fish tank rather than simply changing out the water. Use the scrubber to gently scrub the sides and bottom of the tank where you see algae.