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At what stage of the filter should the UV go?

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  • At what stage of the filter should the UV go?

    Just wanted to get peoples opinions on UV and the correct placement of it. I have heard of place UV's in their settling tanks and have heard of people place them on the return to the pond after the Bio.
    The world sleeps as the chance to learn something new passes.
  • #2

    Easy the skimmer where it sees the upper layers of water (that would tend to have the most floating algae), requires no special plumbing, generates no additional backpressure on the pump, and costs less (as there no standalone housing for it).

    Koi keeping is not a belief system; it is applied science with a touch of artistry.


    • #3

      Both places are seemingly appropriate.

      After everything is an easy place to retrofit. Mostly because most UVs are designed for pressurized situations.

      In the skimmer is also fine, as long as you remember to leave it off when the pond is just starting and you don't want to kill any beneficial bacteria that might be floating through (you want the bacteria to seed your bio-chamber(s)).

      The reason against skimmer/settlement chamber is that dirty water can reduce the effectiveness of the UV rays. But with strong enough UV it shouldn't be a problem.


      • #4

        I thought the rule-of-thumb is that you always put the UV after the last stage of filtration or wherever you have the cleanest water. The maintenance issue with UV is fouling of the quartz sleeve so you want to minimize the gunk passing through it.

        -steve hopkins


        • #5

          Good subject, has anyone in more temperate climates (Hawaii, Calif., etc.) able to maintain clean/clear water quality without the use of a UV? Are there water qualities that cannot be had without a UV system in place?


          • #6

            UV lights have been placed in the settlement chambers of the japanese at the beginning of the filter system, while european, american hobbyists tend to place them at the end of filtration as they dump back to the pond.

            I don't use one and my water is crystal.

            bulbs need to be changed on an annual basis and the sleeve cleaned as well.

            I believe the reason in different parts of the world useing different placement is because they have a different purpose. In the states, it's to control green water.
            in japan it's to eliminate bad bacteria before it gets thru out the system.
            Dick Benbow


            • #7

              or just skip the UV and do ozone...

              Koi keeping is not a belief system; it is applied science with a touch of artistry.


              • #8

                Akai-San: I used UV a few years ago, but stopped when I realized the water was clear and the UV had been unplugged for a month. I do not have the truly perfect clarity that can be accomplished, but when the pond was shaded by trees it was as clear as any I've seen in the area, excepting one. Now that it is in full sun most of the day, there are bits of algae that slough off the pond walls. These fine filaments cause me to think of the water as less than clear, but non-fanatic visitors think it is clear. I think my relative "success" is due to the carpet of algae on the pond walls and floor inhibiting competitive algae growth in the water column, together with sufficient filtration that ammonia and nitrite are never an issue.

                I'm hoping things will stay as good when the new pond gets constructed, because one corner I cut to save money was: no UV.


                • #9

                  Once you have an ecologically balanced pond and a mature filter system, algae only becomes a problem in extreme cases of pond shallowness (less than 6 feet, no shaded areas), or extreme sun exposure (warm water at the surface).

                  Algae are very ancient species that have the ability to put in the water inhibitors for the other types of algae (2000 or so :-). I keep telling people that they have to choose which type of algae they like best and KEEP it.

                  New pond syndrome will always bring about monocellular algae (the green soup). A little of it is not harmfull but al lot of it is (especially if chemicals are used to kill it all at once). I recommend a UV clarifier on new ponds, for the first 2-3 years.

                  After 2 years, a good filter system should have matured enough to host heterotroph bacteria that will take care of algae in most circumstances. I had one instance last year where I had to turn the UV back on to eliminate an infestation of diatoms (grey suspended algae).

                  I hope this helps,


                  • #10

                    Akai-San, it's probably easier to keep clear water in areas without a severe winter. Without the seasonal cycles, the pond stays much more stable. On the mainland, it is common to get an algae bloom in the spring when things start to come back to life. To a lesser extent, that happens in Hawaii as well. Nelson mentioned that it happens to him but disappears pretty quickly. I get a light algae bloom when the monkey pod leaves fall and the sunlight increases in February-March. Otherwise, that pond is too shaded to keep a good carpet of algae on the sides of the pond so it cannot cope with the sudden influx of light.

                    I agree with Authur that a little green water does no serious harm and the only real danger is when it gets thick and then all dies at once due to chemical eradication or a natural population crash. Were it not for the koi observation issue, a little green water may actually be beneficial as it supports a food chain of forage items.

                    -steve hopkins


                    • #11

                      Well I put mine in the settlement chamber. The reason is that I use the fluorecent type, which according to the recomendation, has to be placed close to the water level. Should I put it in the last chamber, then if there is a power failure, it will be submerged in the water, as the water level in the last chamber is always lower compared to the first chamber.


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