Is green pond water bad for fish?

Green pond water is not bad for fish. It is actually making the water safer for the fish. The water goes green because there is not enough nitrifying bacteria in the pond.
This is easily fixed by adding more biological filtration (which provides more homes for the nitrifying bacteria) or adding more bacteria manually to the pond.
The best biological filter in my opinion is a bog filter. They can be easily made yourself nice and cheap. Best of all they are low maintenance and provide crystal, clear, fish safe water.
Here are some links to help you learn more about biological filtration and nitrifying bacteria.
https://youtu.be/yDENqUdij6c- Quick guide to the nitrogen cycle
https://youtu.be/-pg6lzVG_8w- A quick overview on bog filtration
https://youtu.be/CQDVwnlGkGI- What happened when i added a bog filter to my fish pond.
https://youtu.be/669ZWk3pBHw- What size should a bog filter be?
https://youtu.be/oLOPqNN0vJo- Bog filter flow rate

Видео Is green pond water bad for fish? канала Ozponds