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Thread: UV light needed for koi pond?

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    Nathan Tran is offline
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    UV light needed for koi pond?

    I turned off my UV light then forget to turn it back on for two weeks. I just found out last night but my water still gin clear. Any boby out there not using UV light at all? Water temp: 85-90 in Houston

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    If the pond is well established with enough good bacteria you can get by with no uv.
    Tom





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    UV turned off this summer and crystal clear water , water temp this year with DIY bakki shower is around 77. but during 2 weeks water became quite green and turned back after to clear
    The sign is wherever the sun shines

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    I am going to build another pond for my brother next year. I am trying to test if I could get away with the UV system ($400 in saving).

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    If you have enough filtration and the right filtration and some limits to the amount of sunlight your pond receives- you don't need a UV light. I haven't had one for 6 years.

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    this time of year when your bio is at its max, you can try and turn off the UV. if you have very good bio the algae will have nothing to eat ...but you will want it in April/May when the bio is down from the winter and pond is coming back to life..

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    A new pond in particular, and existing ponds during the spring, have little or no bio filtration. The green water algae needs ammonia. Consequently, as you go through the cycle in the spring, or in the development of a new pond, it is common for a pond to go very green. Early in my ponding I was told do not treat for algae, it will just return, and do not dump the algae water and fill with fresh water, as it will just turn green again. As soon as the bio gets up to speed to match the fish load and fish feeding, then the water will clear by freaking magic, as one web site once said. The UV will provide some minimal additional polishing of the water, since there will always be some background green water algae, but it is not absolutely necessary. I consider uv more important on a new pond than an existing pond.

    I run my pond year round, and with the aid of heat, I am able to feed year round, so the filters stay up, though they still cycle with additional activity and food as the pond warms. I sometimes forget to plug the uv back in and can rarely tell the difference.
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    Quote Originally Posted by Nathan Tran View Post
    I turned off my UV light then forget to turn it back on for two weeks. I just found out last night but my water still gin clear. Any boby out there not using UV light at all? Water temp: 85-90 in Houston
    I ran mine in the spring, it was a brand new pond. Water never went through the all green stage.
    Haven't run it all summer and water still looks great. I think the fact that my pond is under trees helps. That and the bog.

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    This Norm Meck article has probably been quoted many times here, but worth a read for those interested in green water and clear water.

    I come from a water garden background more than Koi pond, but I've found that a UV is often only needed for a few weeks and then can be turned off for months, even years. But that's a water garden. In addition to Norm's theory I have a theory that macro and micro algae produce chemicals to kill each other. The UV kills the micro algae giving the macro algae a chance to grow and produce the chemicals, called allelochemicals and so the micro algae can't return. Pretty common in the plant world, and well studied in saltwater algae but not with freshwater algae. But I think it's a reasonable theory. Could explain the chemical Norm saw in clear pond water that killed algae.

    Some Koi ponds are kept spotless so keeping water green free wouldn't work for this theory. Might still for Norm's theory.

    There is a difference between reducing algae and clear water imo. Nutrients and light can be used to reduce algae but you would still have green water, just not as green. Clear water is a different phenomenon entirely. This clear water actually kills unicellular algae almost on contact as Norm showed. With clear water you can add as much nutrients and light as you like and unicellular algae will not grow. A difficult theory to prove but I have tried experiments and wasn't able to grow macro and micro algae together for very long. One or the other ended up winning. Not really proof, but I've found it reasonable.

    To me it explains why TT and streams often are credited for clearing a green pond. The thin water over the rocks give the macro algae a foot hold. Normally the TT is given credit by reducing ammonia, nitrates or other nutrients, but I often read that the person's TT is also covered in string algae which is rarely given the credit.

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    I had a gravel bog filter+Plants for 7 years in the past. I did not used UV light at all, the water was clear. I changed my filter system to 55 gallon drum sand/gravel filter but why would people recommended me to put in a UV light with new system?

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    doesnt a uv kill the bad bacteria though

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    The UV will kill bacteria, good and bad. The problem is that the bacteria multiply faster than most ponds can circulate the water through the UV, and for many of the bacteria, the dosage is way higher than that needed to kill algae, which is the design of the unit. If you slow the unit down, it kills what goes through it, but the flow is too slow to get the amount of turnover needed.
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    Quote Originally Posted by Nathan Tran View Post
    I had a gravel bog filter+Plants for 7 years in the past. I did not used UV light at all, the water was clear. I changed my filter system to 55 gallon drum sand/gravel filter but why would people recommended me to put in a UV light with new system?
    Personally, I like having the option... if I don't need it, I turn it off, if I want to clear the algae quick, I turn it on. That's why I have two.

    New water with a new system will often turn green... if you don't mind it, then don't put one in... but I think that's why it was suggested.

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    I don't have one and never did and the water is clear enough to see anything on the bottom at a depth of 5 feet.

    Yorkie
    A true pondaholic!
    40,000 Gallons, 45 koi




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    I learned the hard way $$.....my pond needed a heavy salt tx....I didn't realize it but the Bio started all over again....turned green bad....on and off for 3 mos. Decided to bite the bullet and get my UV fixed, ended up just getting a new one instead. Learned in the process that the algae was using the ammonia up as food, would deplete the food supply, start to die off and then when the ammonia rose again it would go green again....Needless to say...2 days before my brand new unit arrived....it went crystal clear, like magic.....I haven't put the new UV on, but I still have itl. The curious thing to me was that my water paremeters stayed good upon testing....ammonia never read high...I guess the plus there was that the algae kept the water safer for the koi....I'm in sunny hot Florida....The pond is in the sun,,,water temps I bet are 85-88 at least...since we don't go through a spring start over here I bet I would have been just fine without it.....
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