Originally Posted by
Dravin
Just because your water doesn't get green doesn't mean someone else's pond won't. Nothing is wrong if your water get's green. The fact that you don't use a UV and your water doesn't get green tells me that you either live in an area which is rather cloudy, your daylight hours are not as long as other places, the water isn't 70+ degrees, or you have shading over your pond. If you live in Colorado where with have 300+ days of sunshine a year and it's light from 5:00am to 8:30-9:30pm, you can't stop your water from turning green without a UV light or shading your pond. It doesn't matter how great your filtration is, you can even do 30% water changes every day and the water will stay green. You can have a turnover rate of 5 times per hour in your pond filtration unit---algae will convert much of the ammonia before it gets to your filters if your pond green.
So, consider yourself lucky that you do not need to deal with algae---others are not as fortunate.
On the topic of whether green water is good or not, it's a natural way to protect the koi from sun, and it does a good job assisting in biologically filtering your water. I'm not sure of the science behind it but supposedly green water is really good for the koi's skin or so the breeders have told me. Huge downside---you can't see your koi. Minor downside, if you don't feed color food and your water get's too green it can actually cause your beni to lighten up temporarily due to blocking out the sun.