Green water is generally considered to be the biggest problem with water gardening. Being able to see your fish swimming at any time is always desired, but becomes a challenge when the water quality becomes questionable. Green water should be a warning that something is out of balance with the water. Most people think that high ammonia levels are responsible for green water, this is not true. Phosphates are the reason green algae rears its ugly head in the water.
There are a few ways to clear the water of algae. Improve the water quality, add ultra violet lights and ozone.