UV Sterilizer low flow impact

[Johnseye]

My 1.5" return plumbing has a wye just after the return pump supplying a 1" manifold. As of today I have a single 230w Red Dragon RD3 providing the return flow at 210w. The manifold can feed a couple reactors if necessary but they are not in use today and those valves are closed. It primarily feeds my chiller through the 1" pipe. Yesterday I added an Aqua UV 57w UV sterilizer to the manifold before the chiller. I had no idea what the flow would be through the manifold so I also added a gate valve and a Neptune flow sensor before the UV sterilizer. I thought I'd need to decrease the flow, but it appears that's not the case.

My DT is about 260g. Recommended flow for this sterilizer is 3x, so 780gph. If you factor in the sump volume I'm looking at about 1,140gph as 3x. According to the Neptune, the flow I get through the manifold is about 325gph. That's essentially 1x. What is the impact of 1x turnover? I would guess it means it could take approximately 3x longer to do the job at a higher flow rate. I would also guess the UV power will kill a lot more, if not everything going through the sterilizer at that rate. Aqua UV's instructions state a higher kill rate will kill the planktonic food effect of the reef. I will be calling them today, but am wondering what people's personal experience is.

Thanks

 

[AZMSGT]

Recommended flow for this sterilizer is 3x, so 780gph.

That doesn’t sound right.
UV Sterilizers are rated in terms of ideal and maximum flow. So for instance my 40w is rated at 157gph ideal to 262gph maximum to effectively sterilize protozoa.
I had to use a valve to adjust the flow rate from the UV.

 

[Johnseye]

That doesn’t sound right.
UV Sterilizers are rated in terms of ideal and maximum flow. So for instance my 40w is rated at 157gph ideal to 262gph maximum to effectively sterilize protozoa.
I had to use a valve to adjust the flow rate from the UV.

Per the Aqua UV instructions.

 

[ca1ore]

Do you actually have any live, water column plankton in your system? If the answer is no, as I would expect it to be for the vast majority of systems, it’s a red herring.

 

[Johnseye]

Do you actually have any live, water column plankton in your system? If the answer is no, as I would expect it to be for the vast majority of systems, it’s a red herring.

Live copepods and phytoplankton.

 

[dwest]

Live copepods and phytoplankton.

I run that same sterilizer in my 180 as a result of dinos. I run it slowly at about 200 gph. My pod population is as good as ever. Can’t speak for phytoplankton.

 

[ca1ore]

Live copepods and phytoplankton.

Copepods aren't water column swimmers so they are unaffected by a UV. Do you have sustainable phyto or are you just adding it as target food? If the latter, UV won't have much impact either.

 

[Johnseye]

I run that same sterilizer in my 180 as a result of dinos. I run it slowly at about 200 gph. My pod population is as good as ever. Can’t speak for phytoplankton.

This is very good to know, thanks.

Copepods aren't water column swimmers so they are unaffected by a UV. Do you have sustainable phyto or are you just adding it as target food? If the latter, UV won't have much impact either.

Pods in the sump (and DT), phyto goes into the sump with spread to DT and pods living there. I don't have sustainable phyto growing in any attached reactor at this time. If phyto does die by the UV then this just limits the impact of what I feed via the sump.

 

[Johnseye]

I spoke with Aqua UV support. They said if the sterilizer isn't getting 3x flow it won't be as effective in "changing the dna" or killing the organisms. My understanding based on what they said is that the breeding rate of the organisms can exceed the impact the sterilizer is having on their population.

As to the impact the light has on the organisms in the water flowing through at a slower rate, their support was unclear. They repeated the statement in the instructions about coral food source from plankton being reduced but I don't fully understand or agree. Obviously this doesn't impact photosynthetic activity in the DT. Perhaps if there are some free floating organisms which certain coral feed on there could be an impact. Any fish food or coral food put into the tank, like Reefroids, Benepets or similar are frozen or dried and I would consider not a living organism anyway.

 

[AZMSGT]

UV Philosophy for me is, the UV is most effective doing it's job with contact time. The longer an organism is exposed to it the better. At least that's the way it has always been told to me. So having your water moving through the unit at blazing fast speed is nullifying the contact time.

On a side note, if you are only trying to control algae then the speed can be increased dramatically. I use my UV two fold. 1 to control disease like ICK and Velvet (need the slower speed) and 2. to help keep algae at bay.

 

[Johnseye]

UV Philosophy for me is, the UV is most effective doing it's job with contact time. The longer an organism is exposed to it the better. At least that's the way it has always been told to me. So having your water moving through the unit at blazing fast speed is nullifying the contact time.

On a side note, if you are only trying to control algae then the speed can be increased dramatically. I use my UV two fold. 1 to control disease like ICK and Velvet (need the slower speed) and 2. to help keep algae at bay.

My primary reason is to reduce or eliminate unwanted algae (diatoms) and cyano. I am very careful with QT practices to not introduce diseases but you never know and that's a great benefit of the sterilizer.

I'll run it on the manifold for a few months to see the impact. If it doesn't help I can move it to the return. The reason for not putting it on the return is that I want to keep that flow maximized.

 

[Aardvark1134]

Many recommend a setting 180000 which needs a much slower flow. Usually about 1/6th of the flow for 30000

 

[Johnseye]

Many recommend a setting 180000 which needs a much slower flow. Usually about 1/6th of the flow for 30000

I don't understand the 180000 and 30000 numbers. Would you please clarify?

 

[Aardvark1134]

They determine the max size of the item you are able to kill with the UV. The larger the item the slower the flow must be.
Here a video is easier:

Week 14: Are UV sterilizers worth the time, money and effort? | 52 Weeks of Reefing #BRS160

It's Week 14 of 52 Weeks of Reefing, and this week we are going to talk UV sterilizers. We will discuss what they do and don’t do, setting realistic expectations of how they function, how to size and properly set up a sterilizer, answer some common questions, and show you the installation for...

www.bulkreefsupply.com

 

[rsumner]

I have the 15w version specifically for this reason and here's how I translated the chart. For a reef tank, you want your flow through the UV to be between the 30K and 45K columns. So, in your case, If you have a 57w, you should be pushing between 2100 and 3200GPH through that unit. Anything slower than that, and you may be killing more than you want.

I'm not an expert in UV sterilization at all, but I've been running my 15W between the 45K and 60K numbers with great luck. I run 100% of my turnover water through the UV at around 400 to 420GPH on my 108 gallon display tank. I run it at night on the same cycle as my fuge light and leave it off during the day.

With all this talk of UV, it's probably time I replace my bulb or at least clean it ;-)

 

[Aardvark1134]

The idea that running at 90000-180000 is harmful to your reef has been proven false hundreds of times and by tons of very successful reefers. If fact if you run lower than that you basically turn it into a clarifer instead of a sterilizer.

 

[vangvace]

I don't understand the 180000 and 30000 numbers. Would you please clarify?

180,000 µWs/cm² and 30,000 µWs/cm², or how much UV the particulates are being exposed to. In the chart above, it corresponds to bulb wattage and flow through the unit. 180,000 µWs/cm² in particular for killing Protozoa flowing through it while 30,000 µWs/cm² is more for preventing blooms.

Ideally a sterilizer is more efficient when ran so it doesn't recirculate water immediately. Like having it inline with the return pump going to the display vice on a manifold staying within the sump.

At 325gph, you should easily be hitting the 180,000 µWs/cm² number and then some, which in theory can help but not prevent some diseases. Though at that flow rate it might be too slow to effectively filter all of your water. (Vague enough? Good because UV ;Walkingdead )

For Cyano and Dinos, I would aim for 45k-60k µWs/cm² ( 2100 -1600 gph) based on your UV sterilizer size.

 

[ajslentz]

I’m confused now and have an aqua uv 25 watt on the way so could use some help. I’ve been told the slower the speed the better and don’t worry about killing plantonic anything. O was told to run the water slowly, like 200gph, get lots of contact time and that would kill everything possible. Thoughts?

I’m not trying to oversimplify but I did the same and went through the chart but people keep saying to just let it go slow...

 

[vangvace]

@ajslentz no worries.

The jist is 2 parts:

lower speeds = longer contact time = higher order of creature killed when using a proper brand of UV.​

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The further apart the input and output are the better to avoid sterilizing the same water over and over. Ideally, plumbed inline with the return.​

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The reason not to worry about plantonic life is we doing normally grow phyto in our tanks, but feed through spot or dispersion.

The OP is running a 57W version, your 25W at 200 gph will be somewhere between 90,000 µWs/cm² and 180,000 µWs/cm²