Green Water in fish tank

Yes of course, it's as a result of excess activities of algae in your fish pond that eventually turns the whole water to green color and it's not safe for the fishes in it.

If you have green water when it comes to an aquarium you will find that the culprit is more than likely algae. This can come from a number of reasons including too much light or sunlight. If you are finding that you keep getting it a lot, you could try moving your aquarium away from any kind of direct light or sunlight and maybe try looking into treating your water to help prevent it.

Green water is caused by a sudden explosion in the algae population, and it could multiply even more so try to clean it as soon as possible.

Algae grow in fish tank rapidly with exposure to sunlight. Controlling this exposure can reduce the growth. But once the algae has already grown in water, it has to be removed as soon as possible or it will jeopardise the fishes too.