Green water is caused by a sudden population explosion of free-floating microscopic algae, phytoplankton. It’s usually caused by excessive light, nutrient imbalance or poor maintenance.
The most effective way to get rid of the green water is to install an Ultra-violet Sterilizer in your aquarium. As the water passes through the UV chamber, the algae is killed by the Ultra-violet light. You will want to keep it on for 3-7 days, depending the the size of the aquarium and the rating of the UV sterilizer.
Another method is to use the algae eating organism, like Daphnia. The process will take time as it takes time of the Daphnia to reproduce enough population to consume the algae.
