UV or not UV

[Cdsdave]

I currently have a 4000 gal. tetra bio filter with an 18 watt UV light. I have left the UV on since the pond (2000gal) has been in existence (4 months). I currently have algae causing the vis in the pond to be about 1 ft (3 ft max depth in pond). My pump is 4000 gal max. I'm not sure if the water is flowing over the UV too quick or if its just not powerful enough to kill the algae. Should I consider getting a larger unit to clear up the algae? If so what size considering pump and pond size? Thanks!!

 

[fishin4cars]

If the UV worked for four months and just now starting to get green I would see what the cost were to change out the bulb, tetra bulbs usually aren't expensive, but they don't last that long either. 6 months of use and they have pretty much used up the light band that kills the algae cells. I would also be looking at filtration to stock load, does the pond have plants? If algae is starting to cloud the water there is usually an abundance of some nutrient that is causing the bloom, lack of water changes, over feeding, crowding are some of the things that can cause this, There are others as well.

 

[dieselplower]

Could be any or all of the above! It does seem like that is too much flow through not enough watts as well.

 

[Dave 54]

We have a 36 watt Aquapond U/V-C that last 2 years which are very similar to your own U/V-C to be honest I would say its your bulb that needs changing plus I'vea feeking that yours isnt beefy enough to do the job you want it to do .
Perhaps an pgrade maywell be the answer .

rgrds

Dave

 

[Cdsdave]

My water has been greenish for about a month. I'm thinking of upgrading and shutting off the uv onthe bio filter . What strength/size should I be looking for considering my flow and pond size? It seems there are different opinions out there. I would like to be able to kill pathogens as well. That does require a stronger wattage then just killing algae cells correct? Lastly I saw on a you tube video that its ok to install the uv before or after the bio filter. I thought it was supposed to be after the bio filter?

I appreciate all your input fellas!

 

[Dave 54]

My water has been greenish for about a month. I'm thinking of upgrading and shutting off the uv onthe bio filter . What strength/size should I be looking for considering my flow and pond size? It seems there are different opinions out there. I would like to be able to kill pathogens as well. That does require a stronger wattage then just killing algae cells correct? Lastly I saw on a you tube video that its ok to install the uv before or after the bio filter. I thought it was supposed to be after the bio filter?

I appreciate all your input fellas!

We personally dont rate the tetra U/V-C's we use an Aqua Pond U/V-C it's a 36 watt one with a double bulb that last for 2 years its very similar to the tetra ones in body shape. but is higher in wattage
Our's is in llne after the biofilter and Oase 3500 pump.
It keeps the pond clear of Algae no problem ..........tell me you dont switch it off for anyreason ?

rgrds

Dave

 

[Waterbug]

The Tetra 18 watt is rated as a clarifier for up to a 4400 gal pond. So you shouldn't need a larger unit. Clarifer is an ambiguous term, but given your pond is less than 1/2 the rating you should be fine.

The max flow thru the unit is rated at 2200 GPH. You say your pump is "4000 gal max", I assume that means 4000 GPH. I don't know what kind of head you're running, but probably pretty safe to say you're way above the 2200 GPH max flow.

So I'd try turning down the flow to the UV. Even if you weren't above the max flow I'd still recommend turning down the flow and see if the green goes away in 5-7 days. Turning down the flow can also make up for an older bulb for a unit like yours which is plenty enough watts. If you had something like a 9 watt turning down the flow isn't really very helpful in extending a bulb's useful life because it has to run at near 100%. I'd be shooting for about 1000 GPH. So the flow coming out of the UV should be about 1/3 of the flow coming out of the bypass.

If you don't already have a way to turn down the flow consider that if you buy a new unit you'll still have to (or should) install a valve to control flow. So adding a valve to your current unit doesn't really add cost or work since you'd have to anyways.

6 months is the useful life of the bulb, but you still should have some useful life there. No reason to buy a new bulb at this point until you at least try lowering the flow. And you only have a couple months remaining in the season for using the UV so it should get you thru.

 

[crsublette]

It probably worked, or is still working, except it can not zap the water well enough to kill the density of algae passing through the UV chamber. So, the algae quickly regrows what the UV zapped.

Water turbidity will decrease the performance of the UV device.

Make sure there is no thin film buildup on the bulb.


Yep, as others have suggested, before buying a new bulb or entirely upgraded, I would install the UV on a bypass line that runs parallel with your main line, a valve on the main line. Close the main line valve will push water into the bypass UV line and this will give you longer usage out of your bulb by slowing down the water. I am told the flow rate through the UV should be at least twice an hour, but I imagine this all depends on the density of the pea green water algae.

If the pump is originally rated at 4,000gph, then you are quite likely only getting around 3,500gph out of it or only 1,000gph out of it, that is depending on your filtration system (whether it is pressurized or not) and pump (whether it has a low or high head height rating). The pump manufacturer's rating on it does not necessarily mean it is the actual flow rating; to understand why, then read post#17 at bottom drain, plumbing, and pump advice needed.

Also, as Waterbug mentioned, the Tetra 18 watt is rated for 2,200gph. If we are to assume the pump's actual flow rate is near 4,000gph, then this is definitely too fast for the Tetra 18 watt and especially so after the bulb has been in operation for a while.


The problem I have with these lower rated UV bulbs is that they often are of lower quality, that is they emit much less than 22,000µWs/cm², which is what is required to kill algae. Also, with how the chambers are constructed, with these lower quality constructions, quite likely only around 50~80% of the UV bulb is exposed to water, which means you are not getting the full use out of the bulb. If Tetra were to share this information, then I bet ya their light spectrum is only around 1,000~3,000 µWs/cm², but, after looking at the product at Tetra, they appear to be constructed where so that 90% or so of the bulb is exposed to the water although the small chamber does concern me. So, I bet Tetra compensates by initially starting out with a mucher slower flow rate recommendation for the bulb from the getgo. Also, here is the product manual for the Tetra 18 watt.

Also, I truely doubt the bulb will last a full 11 months of usage, which is what the documentation suggests.


If wanting to get a new UV device, then check out the thread what size UV? and I would always choose one that is oversized.

 

[crsublette]

I currently have a 4000 gal. tetra bio filter with an 18 watt UV light. I have left the UV on since the pond (2000gal) has been in existence (4 months). I currently have algae causing the vis in the pond to be about 1 ft (3 ft max depth in pond). My pump is 4000 gal max. I'm not sure if the water is flowing over the UV too quick or if its just not powerful enough to kill the algae. 1) Should I consider getting a larger unit to clear up the algae? 2) If so what size considering pump and pond size? Thanks!!

1) Should I consider getting a larger unit to clear up the algae?

For UV devices, bigger is always better. The limit is whatever you believe is reasonable for your budget.


2) If so what size considering pump and pond size?

Choosing UV size depend's on a few questions. What is very brief and concise description of your plumbing and filtration system?? What is your pump's flow rate and head height ability, as indicated by the manufacturer's product details ?? Can you water flow meter the water at the end of your filtraiton system ?? If these questions can not be sufficiently answers, then it is just a guessing game.

If your pump is rated for 4,000gph, then lets assume it is only giving you 3,500gph. It seems the trend of these cheaper UV devices is to have 80~240gph per watt. So, anywhere between a 14~45 watt UV device would work for ya. To get better performance and longer lifetime, then I would go bigger and closer to the 45 watt range. Also, install valves so that you can get more usage out of it as the bulb ages.

 

[Cdsdave]

My pump is a Euro P series I purchased from koi enterprise. It's rating is just under 4000 gph. The head I'm running is roughly 4 ft. I leave the UV plugged in 24/7. My Tetra filter is pressurized with the UV built into it.

I'm considering an Aquaultraviolet 57 watt with wiper since I want to kill pathogens as well. I figure with that rating my flow should be fine without installing a plug. Plus hoping to do as little plumbing as possible. I don't mind the work just feel the fewer parts/connections the less chance of leakage. For ease of installation it would make more sense for me to put it before the bio filter, but if slowing down the flow would help even with that size unit I will put it after.

 

[Waterbug]

There are indeed two ways to adjust flow rate. One way uses about $30 in plumbing fixtures so flow can be adjusted. Another way is to keep buying larger and larger UV units until you get the right size for whatever flow you happen have. That cost hundreds, even thousands of dollars and normally requires even more re-plumbing than adding flow control. Given two options most people do seem to choose the most complex and expensive. I have no idea why. Maybe it's hobby funness.

The concept of a UV killing enough pathogens to matter is reasonable in a very controlled environment like an aquarium. Even in that environment most experienced aquarists consider a sterilizer to be a help, not a cure of anything. A pond environment...good luck.

 

[crsublette]

There are indeed two ways to adjust flow rate. One way uses about $30 in plumbing fixtures so flow can be adjusted. Another way is to keep buying larger and larger UV units until you get the right size for whatever flow you happen have. That cost hundreds, even thousands of dollars and normally requires even more re-plumbing than adding flow control. Given two options most people do seem to choose the most complex and expensive. I have no idea why. Maybe it's hobby funness.

The concept of a UV killing enough pathogens to matter is reasonable in a very controlled environment like an aquarium. Even in that environment most experienced aquarists consider a sterilizer to be a help, not a cure of anything. A pond environment...good luck.

I do not believe anyone here is suggesting UVs are a cure for anything. Even the green water algae with a proper UV, I bet there are still reminants of it existing in the pond.

Since the UVs are plenty capable of decimating the floating pea green algae, that is in a pond environment, then I do not know why it would require a leap of faith to suggest a properly rated sterilizer, with correct flow, would also decimate the pathogens, bacteria, viruses, and other weak parasites that are susceptible to it. Due to its quite significant impact on the floating planktonic algae, then It would seem common sense and more logical to suggest there will at least be a noticeable impact on these other entities with a properly rated sterilizer with correct flow. Again, due to the impact on algae spores, I am failing to see the logic trap of suggesting sterilizers actually do not have any noticeable impact on these other entities. Of course, since we're both being subjective in using quantitative terms that require measurement, at either end of this debate, we will never know without proper lab testing the water.

I know folk in the "for-profit" commercial aquaponics get these UV sterilizers just for the peace of mind and CYA to indicate they are doing everything to keep the environment safe for healthy food production. That's good enough for me unless there is actually a persuasion out there that discounts it.

Also, since the bigger UV devices allow for better operation at higher flow rates, then the higher pond turn over rate through the device is more likely to have a better impact at controlling these other entities.

 

[crsublette]

My pump is a Euro P series I purchased from koi enterprise. It's rating is just under 4000 gph. The head I'm running is roughly 4 ft. I leave the UV plugged in 24/7. My Tetra filter is pressurized with the UV built into it.

I'm considering an Aquaultraviolet 57 watt with wiper since I want to kill pathogens as well. I figure with that rating my flow should be fine without installing a plug. Plus hoping to do as little plumbing as possible. I don't mind the work just feel the fewer parts/connections the less chance of leakage. For ease of installation it would make more sense for me to put it before the bio filter, but if slowing down the flow would help even with that size unit I will put it after.

Hmmm. I could not find a flow chart for the pump you are describing. The pump's flow chart would give you a good indiciation on how quick your pump's flow rate will reduce when it encounters resistance.

Yep, makes sense behind your reasoning. Also, bypass lines add to your friction loss and thus reduces your actual flow rate, whether be it a small reduction or not. I would much prefer inline UVs as well. Although, you will get more use out of the bulb over time with a bypass.

 

[Jason]

Interesting, I don't know much about UV wattage vs Gallons but I have a 13w UV in my filter being pushed by 900gph and the only algae I have in my 500 gallon pond is what grows on the rocks, hope that helps.

 

[Mucky_Waters]

Waterbug's reference to the use of UV units is exactly why I felt better going with a higher UV wattage for my pond. Mind you I didn't have to pay hundreds or thousands of dollars, in fact I paid less than $100 for a 55 watt unit (including and extra bulb), which is about what most people pay for their 11 or 13 watt units. So given that you can buy a decent 55 watt UV for about the same price you can buy an 11 watt unit, why not go with the 55 watt-er?
Here's the UV I went with. It doesn't come wrapped in a stainless steel housing, but it has been working fine for me anyway. They really aren't that complex a device. The basic function is that water has to flow past a UV light, that's it. As long as it can accomplish that without leaking you have a functioning unit, there is no need to spend thousands on something built to withstand a mac truck driving over it unless you plan on winter storing your unit in the middle of the road . The bulb is basically the only wearing part on them, and the expensive unit's bulbs will wear out just as fast as the cheap units, in fact they probably use the same bulbs. Something else to keep in mind is that a 55 watt unit functioning at half capacity will still working better than a 11 watt unit functioning at full capacity, which is possibly another reason to get a higher wattage unit from the get go.