The power of UV

[koibooi]

When I build my first 30 ton pond about three years ago I installed 3 x 50watt UV lights. Over time I changed the UV tubes about once a year and have never had any green water problems even though the pond is in full sun. Water temperature where I live in SA seldom goes below 18 Celsius but can get to 29 Celsius.

From the beginning of October this year I started having green water problems. I replaced the UV tubes and it still did not go away. It got so bad that I did an 80% water change but a few days later it was back. I tried all kinds of pond treatments but it would clear up for a day and then be back again.

At this time I also commissioned an 8 ton quarantine pond. I did not connect the UV straight away as the electrics were still being finished. About 4 weeks after filling, the water also started going green. Once the electrics were completed the 15 watt UV went on and 2 days late the Q-pond water was clear.

This caused me to re-look at the main pond UV's. First thing I noticed was that the tube was not burning as bright as the Q-pond. Upon opening the ballast, I saw that water entered the controls and rusted the small transformer. Checking the other two UV's revealed the same.

I bought 3 new 55 watt UV units and installed them and two days later all my green water problems were gone. Never again will I question the effectiveness of something as simple as a UV. So the lesson is that should your water be turning green when your pond comes out of its winter sleep, make sure that your UV lights are burning bright.

[Russell Peters]

Quote: Originally Posted by koibooi When I build my first 30 ton pond about three years ago I installed 3 x 50watt UV lights. Over time I changed the UV tubes about once a year and have never had any green water problems even though the pond is in full sun. Water temperature where I live in SA seldom goes below 18 Celsius but can get to 29 Celsius. From the beginning of October this year I started having green water problems. I replaced the UV tubes and it still did not go away. It got so bad that I did an 80% water change but a few days later it was back. I tried all kinds of pond treatments but it would clear up for a day and then be back again. At this time I also commissioned an 8 ton quarantine pond. I did not connect the UV straight away as the electrics were still being finished. About 4 weeks after filling, the water also started going green. Once the electrics were completed the 15 watt UV went on and 2 days late the Q-pond water was clear. This caused me to re-look at the main pond UV's. First thing I noticed was that the tube was not burning as bright as the Q-pond. Upon opening the ballast, I saw that water entered the controls and rusted the small transformer. Checking the other two UV's revealed the same. I bought 3 new 55 watt UV units and installed them and two days later all my green water problems were gone. Never again will I question the effectiveness of something as simple as a UV. So the lesson is that should your water be turning green when your pond comes out of its winter sleep, make sure that your UV lights are burning bright.

You bring up a good point. I have had many customers have similiar problems and it turned out that hardness from the water had clouded the UV crystal blocking the light. The solution was to clean the crystal.

Some might argue that your green water problem means that you do not have enough filtration.

[Steve Nguyen]

Quote: Originally Posted by Russell Peters snipped >Some might argue that your green water problem means that you do not have enough filtration.

I won't argue but I am one of those who been there and done that and concluded that efficiency of filtration helps reduce algae problem big time.

Steve

[tangigi]

Hi steve,

Am glad I found your thread.

Is there a way to check if the electronic ballast is not effective. I have asked around before and I was informed that as long as the uv lights up, the ballast are working. so I end up assuming its the bulbs that are defective.

I am currently experiencing the same problem you have and its baffling since I have always manage to clear the green water by replacing the old uv lamps.

Thanks

Larry

[tangigi]

Oh, I do clean my aqua uv quartz tube monthly as per instructions.

Larry

[koibooi]

In my case there is definately not a lack of filtration nor do I have too many fish in the pond. I have a seriously big filtration system holding 400 liters of K1 in two Nexus's as well as a trickle filter holding another 200 liters of bio-balls. The 30 ton pond only hold 15 koi with an average size of 70 centimeters. The problem was definately non-functioning UV's.

I would not agree that if the UV is burning it is working. In my case all three of the UV's were in fact emitting a light. The light was fairly dim but it was on and shining. As soon as I replaced the ballast, using the same UV tube, the light turned from its dull shine to a bright shine.

I do not know if there is a way in which one can measure the output of the transformer in the ballast but I would recommend that you replace the ballast and see the difference on the brightness of the UV. It certainly sorted out my problem.

[MikeM]

In warm climates, nitrifiers have a greater challenge trying to out compete the unicellular green algae in the water column, particularly in full sun. When the environment is optimal for the algae, they can consume ammonia and multiply before the nitrifiers convert it to the less useful (for the algae) nitrate. Heavy shading or UV is needed to get the level of clarity koikeepers prefer.

[schildkoi]

One of my favorite subjects....and one that is not totally understood by many. The replication rate for unicellular algae is dependent on nutrient levels, temperature (water) and sunlight (duration and intensity). Other factors also come into play on a minimal level as well (minerals O2 saturation etc). When the combinations (infinite) of these produse a replictaion rate greater than the die off rate, green water exists. UVs address the die off rate but do nothing to reduce the replication rate.

Equal systems (pond designs) can yield differewnt results in different climates as well based on the water temps and avauilable light. Thus MikeM's comment about shae (which reduces water temp and available light) comes into play.

One thing we typically hear is the amount of filtration. Keep in mind, a filter with "2X" surface space/efficiency can be no more effective than one with "X" if "X" is already efficiently processing the all nutrients being supplied.

Thus, the turn over rate (or amount of nutrients being fed through frequency of such) is typically the "forgotten factor." by increasing the filtration AND improving the turnover rate, the ambient nutrient level is reduced which in turn lowers the replication rate of the unicellular algae. This not only helps to improve clarity, it has the even better result of improving the QUALITY of the water. Remember, clear water is not in and of itself a measure of water quality.

Steve

[koibooi]

Quote: Originally Posted by schildkoi UVs address the die off rate but do nothing to reduce the replication rate. Keep in mind, a filter with "2X" surface space/efficiency can be no more effective than one with "X" if "X" is already efficiently processing the all nutrients being supplied. Thus, the turn over rate (or amount of nutrients being fed through frequency of such) is typically the "forgotten factor." by increasing the filtration AND improving the turnover rate, the ambient nutrient level is reduced which in turn lowers the replication rate of the unicellular algae. This not only helps to improve clarity, it has the even better result of improving the QUALITY of the water.

Logic tells me that if the UV's cause a die off rate that is faster than the replication rate then I will also get clear water. Also, if a filter has e.g. 400 square foot of media (2X) it will be more efficient than a filter with 200 square foot of media (X) even if the latter is turned over twice during the same time.

In my instance the 30 ton pond is turned every 40 minutes. I would hate so see the current, pumps and electricity bill if I had to push that up to turning the 30 tons every 20 minutes.

[KoiCop]

Hello koibooii . . .

I think you missed Steve's point, so please let me try to rephase it.

If the existing filter is already bio-converting all the ammonia passing through it at a flow rate of X, then doubling the filter size will not bio-convert any additional ammonia -- it's already converting all of it that passes through it, and you can't convert it twice - whereas increasing the flow rate will reduce the ambient ammonia level in the pond since more ammonia will be bio-converted per hour.

If the existing UV is is already killing all the unicellular algae that passes through it at a flow rate of X, then doubling the UV's power will not kill any more algae -- it's already killing all of it that passes through it, and you can't kill it twice - whereas increasing the flow rate will reduce the ambient algae level in the pond since more algae will be getting killed per hour.

That's why Steve pointed out that increasing the flow rate will achieve both objectives at the same time -- whereas doubling the filter size &/or the UV power will gain nothing. Make sense?