Do UV clarifiers go bad?

[clark kent]

My pond has an older Pondmaster PUV 4000 pressurized filter with the integral 40 watt UV clarifier in it. The pump moves four thousand gallons per hour through the filter, so the thousand gallons or so of water in the pond is getting circulated through the filter every fifteen minutes. There are only eight small goldfish in the pond, and I'm not feeding them. Water chemistry looks good, ammonia, nitrites and nitrates all < .25 ppm.

Light from the UV bulb is visible through the clear plastic section at the top of the filter. It looks fine.

Now though, after a few warm days, a lot of string algae is beginning to show up on the waterfall and around the edges of the pond. I'm wondering if the UV clarifier could be losing its effectiveness. It's got to be several years old.

I recall reading somewhere on a pond maintenance site that UV lights in UV clarifiers do go bad over time, that they produce less effective energy as they age, even though they look fine. Is there any truth to this or was the guy just trying to sell more UV bulbs?

 

[Mmathis]

I can’t speak for UV for ponds, but yes, they do lose their effectiveness. There is some formula...but math and my memory aren’t very good. I know that when my box turtles were newly hatched (and for their 1st year), I kept them in an indoor vivarium, and I recall having to go through several bulbs to be sure they had the appropriate amount of UV exposure during that time period. I’m sure that you can look up the length of optimal use for the bulbs.

 

[IPA]

The clarifier isn’t going to do much in regards to string algae. It does a great job of keeping the pond from becoming pea soup though. The bulb will become less effective over time but seems efficient enough if your water isn’t turning green.

 

[mrsclem]

It depends on how much you use the UV but if used more than a few weeks, it is recommended to replace the bulb every 1-2 years. The bulb will still light but is not effective.

 

[Kirk44]

I agree it will keep the water clear. I still have to walk around the pond and pull some string algae but I find it kind of relaxing. I change my UV bulb every year as I leave it running the whole season. For me in the north east that's from early April till about the end of October.

 

[Lisak1]

Define "a lot" of string algae... can you pull it out by the handful or the bucketload?

 

[clark kent]

Not even by the handful, just a few small clumps. It's just appeared in the past few days. The algae may just be normal with the warming weather. The pond was here when I bought the house in March. I don't know what to expect with changes of seasons.

AFAIK, the UV clarifier has been on 24/7 for several years. The water is clear, so I guess the light is doing its job. I can even live with this string algae as long as it doesn't get any worse.

 

[Mayank]

My pond has an older Pondmaster PUV 4000 pressurized filter with the integral 40 watt UV clarifier in it. The pump moves four thousand gallons per hour through the filter, so the thousand gallons or so of water in the pond is getting circulated through the filter every fifteen minutes. There are only eight small goldfish in the pond, and I'm not feeding them. Water chemistry looks good, ammonia, nitrites and nitrates all < .25 ppm.

Light from the UV bulb is visible through the clear plastic section at the top of the filter. It looks fine.

Now though, after a few warm days, a lot of string algae is beginning to show up on the waterfall and around the edges of the pond. I'm wondering if the UV clarifier could be losing its effectiveness. It's got to be several years old.

I recall reading somewhere on a pond maintenance site that UV lights in UV clarifiers do go bad over time, that they produce less effective energy as they age, even though they look fine. Is there any truth to this or was the guy just trying to sell more UV bulbs?

I'm just a newbie so don't know for sure but it makes sense to me that the uv only kills what goes through it. Algae, bacteria, parasites, protocols, etc. String algae that's attached does not go through it so how could it be killed?
There is NO residual effect of the uv that continues into the pond (this is good because otherwise it could kill all the attached colonizing good bacteria!)

 

[Chucker's 50]

Unlike regular light bulbs, UV Lamps do not burn out – they solarize. This means that over time they reduce in their light wave intensity to about 60% of what a new UV lamp provides. This point is reached usually after one year, or 9000 hours, of continuous use. New lamps will generate a UV light dosage of near 60 mJ/cm2. Over a year’s period the UV light dosage will drop to about 30 mJ/cm2. This is the minimum dosage needed to effectively kill bacteria. At this point, lamps should be replaced. Almost all UV systems are meant to operate continuously, you can actually significantly shorten the life of the bulb by turning it on and off.

 

[clark kent]

Is this loss of intensity continuous, or does it just "bottom out" at about that 60% of new? Since my water is clear, I have to assume that it's still producing enough UV to kill or reduce what algae is in the water that passes through it, even after years of operation.

I get it that this UV filter won't have any effect on the string algae already in the pond.

 

[BKHpondcritters]

Is this loss of intensity continuous, or does it just "bottom out" at about that 60% of new? Since my water is clear, I have to assume that it's still producing enough UV to kill or reduce what algae is in the water that passes through it, even after years of operation.

I get it that this UV filter won't have any effect on the string algae already in the pond.

Many ponds without UV lights don't have green water, so perhaps your pond has achieved a balance that allows the water to stay clear, even though the UV bulb is (probably) not really working any more?

 

[Chucker's 50]

I have a UV light included in my filtration system for my pond.
Earlier this spring I had it plugged in for about 14 days, after it cleared
my pond of the algae bloom (pea soup green water) I unplugged it and my pond is and remains crystal
clear.
2000 Gallon pond with a 100 Gallon homemade skippy type biological filter.

If your UV Light is several years old you can be assured that it has lost it's effectiveness.

 

[clark kent]

Going out to the pond to unplug the UV filter right now. I'll report back in a few days.

 

[clark kent]

Well, it's been a week, and my pond water is still clear. Obviously that UV filter was having no effect on the water. Regardless, that bulb is beyond its useful life, and a new bulb is over sixty bucks. I'm debating whether I even need it or not.

Additionally, I got a long stick and removed almost all of the string algae. Surprising how easy that was. More surprising is that this stuff originally appeared almost overnight in the pond, but now that I removed (most of) it, it has not come back.

 

[Mayank]

Well, it's been a week, and my pond water is still clear. Obviously that UV filter was having no effect on the water. Regardless, that bulb is beyond its useful life, and a new bulb is over sixty bucks. I'm debating whether I even need it or not.

Additionally, I got a long stick and removed almost all of the string algae. Surprising how easy that was. More surprising is that this stuff originally appeared almost overnight in the pond, but now that I removed (most of) it, it has not come back.

Is there a possibility that the string algae was clarifying your water, absorbing ammonia etc and providing a service? It would be food for the fish too right? Unless it was excessive but without a photo I guess there is no way to tell?