The Gray Area of Flow Rates for UV Sterilizers

[Malcontent]

They never receive a lethal dose.
What happens is that the UV alters (destroys) their ability to reproduce. It can kill some but it leaves them sterile. (UV STERILIZER)

Not enough dwell time and they will simply enjoy the pretty violet colored light and continue on with their lives.

Let's say the flow rate and dwell time were such that ich received exactly one birth control dose (BCD). What happens if you double the flow rate and ich receives only half a BCD but twice as often?

 

[sdreef]

The pentair uv is one of the companies with the most precise flow rate recommendations for specific purposes that I've seen. I have been wondering about the flow rates between the 2 specific uses which is why I started this thread. I was just wondering what everyone's thoughts were on this topic and so far it has definitely been interesting and informative!

Pentair recommends 180,000 µW/cm2 as a target. They list a max flow based on 100% output and a recommended flow rate based on 80% at the end of the lamp's life. Aqua UV, on the other hand, targets 75000 - 90,000 µW/cm2 to control fish disease for their recommended flow rates. Lifegard provides flow rates for 30,000 µW/cm2 and doesn't provide a flow rate for fish disease, but easy to calculate based on the dose of UVC you decide to target.

If anyone has a good reference for a target dosage to kill ich, please share. I just haven't found good data and don't know where the manufacturers extrapolate their target values from. Some papers have listed doses as high as 800,000 µW/cm2 to eradicate cryptocaryon irritans theronts (Colornia & Burgess, 1997, p. 233), but again I haven't found any evidence based consensus, and this is well above the dosage the most people deliver or manufacturers recommend.

 

[hart24601]

I think the manufacturer specs are the best we have. However it is more complex than that as the listings are for single pass sterilization, however our systems are closed and that’s where it gets tricky as turnover and the reproduction rate of the particular organism along with its ability to heal from uv damage come into play. As one can imagine this becomes very complex quickly so it’s best to stick with a brand you trust and follow their guidelines as they are variable between companies without any real explanation of differences.

 

[1Clown]

Wonder if anyone runs 2, one for algae and one for parasites?

 

[fishybizzness]

Wonder if anyone runs 2, one for algae and one for parasites?

Thought about it but I'm hesitant due to the heat created by having two pumps and uv sterilizers running at the same time. In reality it could be adding a few degrees to the tank. This time of year would be manageable with a fan blowing on the sump but i live in the Caribbean and in summertime it gets to be a challenge keeping the temps below the mid 80s even with a fan and with the price of electricity i am not running a chiller.

 

[Saltyanimals]

Pentair recommends 180,000 µW/cm2 as a target. They list a max flow based on 100% output and a recommended flow rate based on 80% at the end of the lamp's life. Aqua UV, on the other hand, targets 75000 - 90,000 µW/cm2 to control fish disease for their recommended flow rates. Lifegard provides flow rates for 30,000 µW/cm2 and doesn't provide a flow rate for fish disease, but easy to calculate based on the dose of UVC you decide to target.

If anyone has a good reference for a target dosage to kill ich, please share. I just haven't found good data and don't know where the manufacturers extrapolate their target values from. Some papers have listed doses as high as 800,000 µW/cm2 to eradicate cryptocaryon irritans theronts (Colornia & Burgess, 1997, p. 233), but again I haven't found any evidence based consensus, and this is well above the dosage the most people deliver or manufacturers recommend.

The disparity between leading manufactures like Pentair and AquaUV for target dose supports the higher the better to sterilize thus slowing down flow really increase the contact time and dose power. So why not go very slow and while you may not turn over the water as fast.. again .. is it a race? "Eventually" all your water will flow through this super tube and sterilize all parasites leaving the free floating vs not aside for a moment. What's this argument missing?

 

[Dj City]

The disparity between leading manufactures like Pentair and AquaUV for target dose supports the higher the better to sterilize thus slowing down flow really increase the contact time and dose power. So why not go very slow and while you may not turn over the water as fast.. again .. is it a race? "Eventually" all your water will flow through this super tube and sterilize all parasites leaving the free floating vs not aside for a moment. What's this argument missing?

Your argument does not take into account that these things reproduce.
It's missing rate of reproduction.

Its like if you sterlize 1 while another one reproduces 5.
The UV will never be able to keep up at that rate.

 

[Saltyanimals]

Your argument for not take into account that these things reproduce.
It's missing rate of reproduction.

Its like if you sterlize 1 while another one reproduces 5.
The UV will never be able to keep up at that rate.

Great point, DJ!

Okay.. so some UVs are "improperly" plumbed where it recycles water from a manifold and back to the sump instead of directly going to DT. The situation I think it creates is that you'll have a very highly UV sterilized sump, but not necessarily sterilizing the DT. In a way this creates a UV QT sump. So why not just use this UV QT to house every new inhabitant for a couple weeks before introducing it to DT. The water will eventually make it's way up to DT over time mixing with UV potent water. Thoughts on this argument?

 

[fishybizzness]

I currently have my pentair 40 w uv plumbed with the feed pump in the overflow section of the sump right under the overflow pipe and the outlet of the uv sitting over my filter pad in the second section. Since the outlet is feeding into the direction of the flow in the sump in the section after the overflow i feel that very little if any water from the sump is recirculating through the uv. Any thoughts on this setup?

 

[Saltyanimals]

I currently have my pentair 40 w uv plumbed with the feed pump in the overflow section of the sump right under the overflow pipe and the outlet of the uv sitting over my filter pad in the second section. Since the outlet is feeding into the direction of the flow in the sump in the section after the overflow i feel that very little if any water from the sump is recirculating through the uv. Any thoughts on this setup?

IMO we're both in the same boat as the inefficient plumbing and making the UV QT I described. I plan to plumb in a wye and piping the UV return back to flow.. but that's weeks away while I get other new tank priorities done first. At this point, I have new fish in my sump for about a week to sterilize before moving them to DT. I figured 57 watt AquaUV with 200 gph makes for a highly sterilized sump hence my question above about UV QT sump.

 

[takitaj]

There is no change in the water coming out of the UV regardless of the dwell time. Only the organisms that are exposed to the light, at the required amount of time, are affected. Their DNA is damaged and are effectively sterilized by the UV-C radiation which reduces/eliminates their ability to reproduce, they are not killed. Maybe an 800 watt unit might fry 'em good. lol I don't know about that but again it's not the purpose to kill them but to prevent them from being able to reproduce.

As I mentioned a few posts ago, if you size the UV so that the protozoan rate (ie: ich) is high enough to turn over the tank several times an hour you can sterilize the protozoans and also successfully keep up with the reproduction rate of bacteria and algae. So you can achieve both functions with a large enough UV, based on your tank size/turn over rate.

Ideally you really need to pump either from the tank and back to the tank or from the sump to the tank via the return pump. Either way has to have enough flow to meet the minimum protozoan rate after head loss and losses in the plumbing. I personally tee off an over sized return pump (Varios 8) with valves to divert and control where the flow goes, how much and to also be able to isolate the unit for maintenance/removal. (ball valve at the UV outlet, gate valve at the tee going into the UV and a gate valve after the tee to the tank)

@fishybizzness @Saltyanimals I might not recommend plumbing through the sump like that unless the flow through the sump can exceed the gph through UV. The effective flow rate would be limited by the sump flow rate. In that case just plumb the return through the UV or tee it in with valves as I described. **

**Edit: If you have enough flow through the sump.

 

[fishybizzness]

There is no change in the water coming out of the UV regardless of the dwell time. Only the organisms that are exposed to the light, at the required amount of time, are affected. Their DNA is damaged and are effectively sterilized by the UV-C radiation which reduces/eliminates their ability to reproduce, they are not killed. Maybe an 800 watt unit might fry 'em good. lol I don't know about that but again it's not the purpose to kill them but to prevent them from being able to reproduce.

As I mentioned a few posts ago, if you size the UV so that the protozoan rate (ie: ich) is high enough to turn over the tank several times an hour you can sterilize the protozoans and also successfully keep up with the reproduction rate of bacteria and algae. So you can achieve both functions with a large enough UV, based on your tank size/turn over rate.

Ideally you really need to pump either from the tank and back to the tank or from the sump to the tank via the return pump. Either way has to have enough flow to meet the minimum protozoan rate after head loss and losses in the plumbing. I personally tee off an over sized return pump (Varios 8) with valves to divert and control where the flow goes, how much and to also be able to isolate the unit for maintenance/removal. (ball valve at the UV outlet, gate valve at the tee going into the UV and a gate valve after the tee to the tank)

@fishybizzness @Saltyanimals I might not recommend plumbing through the sump like that unless the flow through the sump can exceed the gph through UV. The effective flow rate would be limited by the sump flow rate. In that case just plumb the return through the UV or tee it in with valves as I described. **

**Edit: If you have enough flow through the sump.

Makes sense. I previously had the outlet of the uv after the first baffle and filter floss but I moved it to over the filter floss because I realized that all the water going through the uv was not being filtered. I think that i will move it back to where I originally had it, after the baffle, and just hang a filter sock on the outlet pipe to make sure I'm filtering all the water going through the sump. With that setup, I will not be recirculating any of the water through the uv as the outlet will be past the first baffle and won't have any way of getting back to the overflow section where the feed pump for the uv is located.

 

[DxMarinefish]

Here's the answer that is correct but you won't want to hear.

There is no grey area. There is no sweet spot.

It's one or the other or neither.
UV MUST be properly sized to the tank.
UV MUST be properly plumbed and it MUST have the correct flow for what you are targeting.
If you miss any of those three requirements, your UV will not work.

For ich and the like, you need the slow flow that is stated by Prntar. It is not a recommendation, It is a requirement. Faster flow will NOT work.

For algae and the like, you need the faster flow that is stated by Pentair. It is not a recommendation, it is a requirement. Slower flow will NOT work.

Slower flow will kill the algae but algae will reproduce and spread faster than the slow flow can handle. The UV will never be able to knock it down with the flow slower than stated and required.

The faster flow for algae will not harm the ich because there is not enough dwell time.

Sorry to be the bearer of bad or unwanted news but the fact is...

There is no sweet spot.

You are correct and I have spent the last few days totally absorbing all the research material I can get my hands on about proper use of UV for specific objectives.

I will now run the UV as per specific objective:

Objective 1 - Algae control (and water clarification) - Run at full recommended flow rate and turn over per tank size.

Objective 2 - Fish pest and disease (those that can be affected by the UV) - Run at full recommended flow rate and turn over per tank size.

I will switch to either as and when needed, but my default will be Objective 1 - Algae control and water clarity.

The UV arrives today and I will need to buy and install a Flow Monitoring device if I can get one.
The ones I have seen in the UK are for Neptune and I don't have a Neptune on my system.

Does anyone know of a stand alone Flow Monitoring device?

Else i will do the old bucket and timer flow measurement and estimate/calculate the flow, and then mark the ball valve so I know were to set it for each of the two objectives.

Does anyone have any other recommendations please?

 

[DxMarinefish]

Will the spores released by Bubble algae in the water be zapped by the UV?
Do different Algae reproduce at different rates and so require specific flow per targeted algae species to be effective, or will an approximation of flow/turn over for the UV be good enough?

Why do UV manufactures have different flow recommendations for similar wattage kit?
I recon the internal design and length of the various UV devices play a part.

I have gone for a UV-C, 80 watt, Long unit for a tank size of estimated 1000-1100 litres.
Flow feeding the UV will be teed off from the return. I use a Vectra L1 as my return. Because I don't have a sump refugium (its dark), i have run my return relatively slow. With ball valves I can divert the required flow to the UV and increase the L1 flow rate to achieve desired flow through.

I am also thinking I will need to time my Return pump service with the Q-sleeve cleaning. Return pumps will loose flow rate over time, and setting and forgetting will not be an option. So as an example, If i service my return pump in January, and install the UV in the same month (doe not have to be same date), I can plan to clean the Quarts sleeve AND service the return pump in 6 months. But the UV bulb is rated for up to 9-12 months. If I change the UV bulb at 6 months, I will not be getting the full usage vs cost. But bulb replacement for the unit I have bought is easy so I will stick to the 9-12 months UV bulb replacement.

I think the return pump service and Q-sleeve cleaning can be synchronised.

I does pose the question though for us with no flow monitor, that by the 5-6 month, the flow will be less than at the start.

Any thoughts?

 

[ADHDan]

after reading through alot of forum posts about UV for ich management and ive been thinking something i havent seen mentioned yet

the big debate seems to be that a certain dose of UV is required to kill an ich theront (swimming stage) and most UV's people are using dont deliver a high enough dose at reasonable flow rates to be effective BUT i havent yet seen anyone mention that while a hobby grade UV might not deliver that killer dose in 1 pass what happens when the ich theront passes through the UV multiple times?
If your UV is powerful to cause some damage to the ich and its passing through the UV 4x an hour then surely its ability to find a host and infect it will be reduced significantly on each pass until it dies of UVexposure or the inability to function and find a host fish.

This is only speculation on my part but makes sense maybe?

 

[ReeferSamster]

What happens to ich that doesn't receive a lethal dose?

They will mutate into the Teenage Mutant Ninja Ich or the X-Ichs.

No seriously, I was wondering about preventative measures for ich with UV. Assuming that you have no outbreak of ich for months or years and do not plan on introducing new water from another tank, is it safe to assume that there are no more free swimming staged ichies, since any that existed never found a host?

 

[Sean Clark]

Just because everyone is at the water park that doesn't mean that everyone goes down the slide. It doesn't matter how many times their friend goes for a ride... it won't convince everyone that they should ride too.

 

[hart24601]

I think the manufacturer specs are the best we have. However it is more complex than that as the listings are for single pass sterilization, however our systems are closed and that’s where it gets tricky as turnover and the reproduction rate of the particular organism along with its ability to heal from uv damage come into play. As one can imagine this becomes very complex quickly so it’s best to stick with a brand you trust and follow their guidelines as they are variable between companies without any real explanation of differences.

after reading through alot of forum posts about UV for ich management and ive been thinking something i havent seen mentioned yet

the big debate seems to be that a certain dose of UV is required to kill an ich theront (swimming stage) and most UV's people are using dont deliver a high enough dose at reasonable flow rates to be effective BUT i havent yet seen anyone mention that while a hobby grade UV might not deliver that killer dose in 1 pass what happens when the ich theront passes through the UV multiple times?
If your UV is powerful to cause some damage to the ich and its passing through the UV 4x an hour then surely its ability to find a host and infect it will be reduced significantly on each pass until it dies of UVexposure or the inability to function and find a host fish.

This is only speculation on my part but makes sense maybe?

Yeah that was exactly what I was driving at with my comment above. I suspect no research has gone into it because it’s too variable and the focus and money for research is single pass for drinking water so those rates are well known. Not only is there flat out killing of the organism but attenuation of it where it’s too damaged to reproduce or infect, and how that is counted is also variable if one is doing a live count for survivors or something like plating bacteria for cfu growing. So I suspect they just stick with what is known.

 

[Saltyanimals]

One year later into my UV and Ich/parasite journey that wiped out my entire 180g tank, my new take away is simple.

Accept that you have bugs in your tank unless you QT 100% of *everything* that goes into your tank forever. Corals, CUCs, rocks, etc. The UV goal really is to keep the populate down long enough to allow your fish to build the appropriate immunity to allow them to fight off the disease. My fish are probably continuing to contribute to the ich cycle, but they're not affected due to this immunity. @Dj City correctly said that one needs to factor in the reproduction rate which is why flow and contact time matter. All to keep the population down as eradication could be unrealistic for a given tank and UV size. This could work if you're talking a massive Pentair unit on a smaller tank, but this is not typical.

I went through great lengths to try and understand and replumbed my entire sump to the recommended placement. Ran in-tank H2O2 which is suppose to benefit from the appropriately sized UV. And I still saw ich on my PBT a month ago. Very little.. but still there.. and the fish is still alive. I only introduced QT fish, but not bullet proof since I don't QT inverts or CUCs. I expect that when I introduce the next batch of QTed fish, that I would immediately see ich return on my PBT due to the stress. However I expect him to live with the ich that is forever in my tank. =)

 

[Chuck310]

Here's the answer that is correct but you won't want to hear.

There is no grey area. There is no sweet spot.

It's one or the other or neither.
UV MUST be properly sized to the tank.
UV MUST be properly plumbed and it MUST have the correct flow for what you are targeting.
If you miss any of those three requirements, your UV will not work.

For ich and the like, you need the slow flow that is stated by Prntar. It is not a recommendation, It is a requirement. Faster flow will NOT work.

For algae and the like, you need the faster flow that is stated by Pentair. It is not a recommendation, it is a requirement. Slower flow will NOT work.

Slower flow will kill the algae but algae will reproduce and spread faster than the slow flow can handle. The UV will never be able to knock it down with the flow slower than stated and required.

The faster flow for algae will not harm the ich because there is not enough dwell time.

Sorry to be the bearer of bad or unwanted news but the fact is...

There is no sweet spot.

I really appreciate your prescriptive answer. I apologize in advance if this question annoys you. I have the 80 watt Pentair for my 340g system. This was recommended by BRS and the team installing the tank. The recommended flow rate thru thus UV for algae control is 2700GPH which will essentially exceed the flow rate of the sump (3000gph Max and I have two active return pumps for redundancy). For the question…on the high end setting of the Pentair is it the static 2700gph OR is it 4.5x your system volume which would make my setting at 1530 (340X4.5) which is MUCH more manageable flow? I would think it is tank turn over for algae control and contact time (1x turnover) for ich, BUT flowing the minimum of 450 for this unit so you do not run the risk of the bulb overheating. Any thoughts?