Saturday, May 9, 2009

It's all becoming clear to me

Last week the Koi Garden pond was a thick and dark pea soup. It was difficult to see the fish at the surface much less when they were submerged near the bottom of the pond.

I then turned on the UV filter.
The UV filter does not work in minutes but it does work.

UV filter setup
The water is pulled into the system via a submersible pump at the far end of the pond. It pulls water through a smaller filter assembly. This filter stops leaves and debris from entering but also has enough filter medium to allow for some biological filtering to take place. The water is then split up into two paths. One path goes directly to the larger biological filter outside the pond. The other path goes through the UV filter and then is returned to the pond via a Venturi tube.

This setup has a number of benefits.

First it allows for some water to reach the exterior filter WITHOUT going through the UV filter. This means that some water will not encounter the UV light and its sterilizing capabilities. This is good. Remember, there is beneficial bacteria suspended in the water that you don’t want to diminish, and the UV light’s sterilizing capabilities does have a negative effect on that bacteria in addition to the algae that makes up the pea soup.

Second, by splitting the water paths, it has the effect of slowing down the water that goes through either filter. This allows the UV light and it’s sterilizing effects more of a chance to have an effect on the water. It allows the UV light more time to sterilize the algae suspended in the water. In the other path, it also allows the water going through the biological filter more time to come in contact with the beneficial bacteria and clear the water.

So after being turned on for 4 or 5 days the water clears up quite nicely. The algae which causes the green water is killed via the sterilizing power of the UV filter. Make sure you test the water both before and after using the UV filter. The algae will feed on the ammonia produced by the fish waste. The UV light will also kill beneficial bacteria as well as the algae. So while the UV filters clear the water up to cristal clear levels, they also might cause increases in the ammonia levels, and therefore Nitrate and Nitrite levels as well.
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