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UV in the 1st vortex

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  • UV in the 1st vortex

    All this time, I used to put UV lights in the last chamber. But since I have some head lost, I positioned it at some distance above water level to prevent being submerged in case of power failure. However, I think this reduces its efficiency.

    So, now I tried moving it to the 1st/primary vortex, where I can place it closer to the water level. But after only 3 days, my kois are more lethargic and loose appetite. Is there a connection? Water parameters are ok, except that it is quite greenish with algae.

    Technically speaking, where is the best place to put UV lights?

    All comments would be greatly appreciated.
  • #2


    We don't have that sort of UV available here in the UK, ours are sealed units which water is pumped through.

    Momotaro use the sort of lamps you are talking about and they recommend they go over the settlement chamber.

    Mark Gardner


    • #3

      Interesting comments mark. As you suggest, alot of the UK and USA hobbyists are used to UV lights that are part of the plumbing and are submerged. Usually they come at the end of the filtration just before returning to the pond. Theory being that you do not want to kill any bacteria from the pond going into the filter, yet you do not want to have
      anything from the filter going back to the pond.

      Yet we know as you have stated the dealer Momotaro uses his suspended lights over the settling sump ( as do alot of other Japanese hobbyists)

      Addressing the problem as presented

      lethargic koi and green water, my head is thinking incomplete filtration
      hence the appearance of the algea. Either his present filter is not is not big enough for the koi load or designed/operated efficiently.

      so....Kiky please help us with more specific info

      size of pond in gallons
      fish load
      water parameters, PH amonnia, nitrate, nitrite, Gh, KH
      Dick Benbow


      • #4

        Hi kiky - Would it be possible that the UV is working better in that position and with the algae dieing off your Water quality is deteriorating? You may be experiencing more bloom at the same time.
        Something I did think about...if the light is just hanging over the chamber will it degrade the chamber(if made out of plastic) itself? I know the PVC that a lot of the UV's here in the states are made out of take a beating by being so close to the UV lamp. Not sure I'd want to have a UV just hanging over the softer plastic our settlement chambers are made of.
        Hope everything settles down for you


        • #5

          Thanks for the information. So it is not wrong to put UV in the 1st/settlement chamber then.

          I agree that my filteration, relative to my stocking level, may not be enough during this time of the year at my place - hot, dry, full of sunshine of 12 to 13 hours every day. Prior to June, when the rainy season stopped, the water was clear without algae. I am busy right now, but I will take water readings in a few days time and be back to you.

          Personnally, I think I agree with your analysis that the UV was simply working better in that position. And dead algae caused the water to deteriorate. I swicthed off the UV lights 2 days ago, and the kois are hungry and active again now! But at the same time the water is turning greener. A strange co-incident?
          My chamber was made of concrete, except for the lower cone-shape part, which was made of a kind of PU fibre (I think, I am not very sure) and about 1.5m below water level. So it should be ok. I was told that UV light will not be effective at such depth.


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