How to control Green water algae in a planted tank

This form of algae is also known as "green pea soup". The water turns into a cloudy green colour.

Common Cause

The primary cause is excess free floating nitrogenous waste coupled with strong light for extended periods. It takes a source of biological waste - a common cause is over-feeding or heavy live foods coupled with poor filtration to trigger it. It takes a lot more filter media to capture free floating particulate matter than to just digest waste ammonia. So tanks that test negligible amounts of ammonia can still suffer from abundant free floating particulate matter that trigger algae.

Green water algae occur particularly in new tanks / planted tanks that are not biologically mature. It is more common in very warm tanks (80f+). 

Solutions

• Mild cases can be cured by over-dosing APT Fix(with care) or by using Purigen as filtration media
• 4 - 5 day blackout for serious cases
• Use Diatom filters
• UV steriliser is a 100% cure for serious cases
• Improve filtering capacity to avoid triggering it again

For detailed steps on how to cycle a tank, click here. 

Tanks that have very good filtration and crystal clear water will find it difficult to trigger Green water algae, even if the water contains ammonia and high light levels are used on the tank.

Tanks with poor filtration with high amounts of free floating particulate matter can get Green water algae easily when strong lighting is used.