Thread: Green water.

You need a UV filter to get rid of green water.

The only other thing I can think of is prevention.

Try creating shade over the pond. That may help reduce it.

Also, If you can use filters that remove/reduce nitrates, this should help. Although it may not stop it entirely as koi pellets and fish waste will add phosphates etc to the water... Which is essentially plant food. And other than water changes I'm not aware of a way to remove phosphates specifically.

Sent from my Pixel 8 using Tapatalk

Rather annoyingly, most biological filters don't remove nitrate, they produce it.

They typically only remove ammonia and nitrite. Well technically they convert ammonia into nitrite and then convert nitrite into nitrate.

Only a few biological filters remove nitrate. For example an anoxic filter removes nitrate, but a moving bed filter won't. An airtight trickle tower would remove nitrates, but a trickle tower exposed to the air wont. Plants would remove nitrates, but a bead filter won't etc...

A shower filter with a very high flow of water over it can reduce nitrates. I understand this is by gasing off the nitrogen. But if you see Slickbe's recent post about his shower filter, he found the reduction to be minimal and he was pumping large amounts of water over his shower.

You could probably get the water clear by having a more natural pond with plants etc and a low stocking level of fish. But most people prefer to have a pond full of big fish. So the only realistic way of keeping the water clear in the latte is with a UV.

I use a 40watt Amalgam UV on my pond. They are expensive to buy, but tend to work more efficiently than a normal UV unit. I only have mine come on for an hour a day (for 13k litres) and it keeps my pond really clear. So the bulbs tend to last longer than a normal UV bulb too.




Sent from my Pixel 8 using Tapatalk

Before UVC ... after UVC...
IMG_1407.jpgIMG_3347.jpg

As you can see I had the same issue. ~14K litres (1.85m deep).

Green water loves nutrients and sun. The pond is in full sun for most of the day and with the original tap water fill - it must still have had phosphates, nitriates and KH - all the things green algae loves.

You could shade your pond, it would help reduce the speed of growth. I tried the chemical options (the dye is why I have a slight blue tint to my window now) but to be honest the UVC was the best option.

I decided to make my own 80W amalgam UVC out of 110mm pipe I had left over and some fittings. The result is I have a second loop from the drum filter inlet side that allows me to pump water (variable pump) through it and back out to the bond. In time I will add a waterfall at the back with that line but it allows me to switch on/off both the UVC and pump. The pump runs at 30W.

Without the UVC+pump on (120W together), my pond only consumes 58W of power.

In the photo it too several days to clear it was that bad! However the fish seem happier.

In terms of running it - I can run for a couple of days and the water is then clear, after which I can switch off for a week or two depending on the weather.

It doesn't stop blanket weed but that's a different story. I can see the fish

As an aside - the green water algae is minute, and as such passes through my 57 micron drum filter. You'd need a very large surface area and a 5-10 micron filter.. I did look into it as an option but in the end the UVC is the simplest and fastest option.