UV flow rate question

[earwicker7]

I've got a Pentair Aquatics 50W High Output Sterilizer in my build, and have a question about the flow rate.

The manufacturer suggests between 260-330 gallons per hour for parasites, and 1560-1980 gallons per hour for algae and bacteria. I have an in-line flow meter, and the pump I have can only get it up to around 1300 gallons per hour.

My plan is to have it set for algae and bacteria unless there is a parasite outbreak of some sort. Yes, I know this won't completely remove parasites, etc., etc., and I have a quarantine tank set up. I asked the builder if I could get a larger pump so that I can get it in the target zone for bacteria, and he says that it's not necessary.

What, if any, negative effects will result from running it at lower than recommended flow rates?

 

[HippieSmell]

Unless your tank is the size of a Koi pond, you'll have no issues. It's best to keep it at a low flow rate anyway, IMO.

 

[ScuderiaDavis]

I've got a 90 gallon with a Aqua UV sterilizer and my flow rate is about 300 gph.

Tank is in tip top shape!

 

[earwicker7]

I wonder if the flow rates have to do with what it doesn't sterilize as opposed to what it does? Algae and bacteria are single cell organisms... perhaps at lower flow rates, it starts to sterilize things which might be beneficial?

This is all theoretical... I just have to think the manufacturer had some reason for listing those values.

 

[ScuderiaDavis]

That's exactly the reason. My LFS sold me the unit and advised me to not get a higher wattage unit because if it's too much, it does start to kill the beneficial bacteria, etc.

 

[slief]

The flow rate impacts contact time. Contact time is what kills or sterilzes what passes through the UV filter. The slower the flow, they high the kill factor. A UV should be sized based on tank size and flow. If you can't reduce your flow enough, a larger UV may be a better choice depending on the goal of the UV. That said, going oversized on a UV Sterilzer is a waste of wattage. In most cases, the same can be accomplished with a properly sized UV fed by a properly sized or gated down pump. And yes, at lower flow rates, you will start to reduce plantonic life which can be counterproductive in the case of a reef if the populations can't reproduce fast enough. I've been running UV's on my systems for decades. Unlike Emperor Aquatics/Pentair, AquaUV has appropriate flow rates for marine and reef aquariums listed for their sterilzers. EA lists flow rates down to 180,000 µw/cm2 which is WAY too low for a reef tank. Even 90,000 µw/cm2 is border line unless the goal is to target parasites in a reef however 90,000 µw will impact planktonic life as well. I usually shoot for around 60,000 µw/cm2 which will keep the water nice and clear while also eliminating bacterial blooms and controlling waterborn algae.

FWIW.. The suggestion of 260-300 GPH for a 50 watt sterilzer is insane. That is 180,000 µw/cm2 + and will kill anything that passes through it including plankton, copepods etc. Very poor advice from the mfg and clearly they don't know what they are suggesting. This has been the case since they bought out EA and one of the many reasons why I would never recommend their products anymore. I wouldn't run less that 600GPH through that thing on a reef. If it's a fish only system, that's a different story. If you want good advice, go with AquaUV in the future. They know what they are doing and will provide sound advice with regards to their products in our applications.

 

[earwicker7]

The flow rate impacts contact time. Contact time is what kills or sterilzes what passes through the UV filter. The slower the flow, they high the kill factor. A UV should be sized based on tank size and flow. If you can't reduce your flow enough, a larger UV may be a better choice depending on the goal of the UV. That said, going oversized on a UV Sterilzer is a waste of wattage. In most cases, the same can be accomplished with a properly sized UV fed by a properly sized or gated down pump. And yes, at lower flow rates, you will start to reduce plantonic life which can be counterproductive in the case of a reef if the populations can't reproduce fast enough. I've been running UV's on my systems for decades. Unlike Emperor Aquatics/Pentair, AquaUV has appropriate flow rates for marine and reef aquariums listed for their sterilzers. EA lists flow rates down to 180,000 µw/cm2 which is WAY too low for a reef tank. Even 90,000 µw/cm2 is border line unless the goal is to target parasites in a reef however 90,000 µw will impact planktonic life as well. I usually shoot for around 60,000 µw/cm2 which will keep the water nice and clear while also eliminating bacterial blooms and controlling waterborn algae.

FWIW.. The suggestion of 260-300 GPH for a 50 watt sterilzer is insane. That is 180,000 µw/cm2 + and will kill anything that passes through it including plankton, copepods etc. Very poor advice from the mfg and clearly they don't know what they are suggesting. This has been the case since they bought out EA and one of the many reasons why I would never recommend their products anymore. I wouldn't run less that 600GPH through that thing on a reef. If it's a fish only system, that's a different story. If you want good advice, go with AquaUV in the future. They know what they are doing and will provide sound advice with regards to their products in our applications.

FWIW, that's only their recommendation for dealing with parasites. They recommend 1500+ for bacteria/algae, so perhaps the lower flow is for fish only tanks.

 

[slief]

FWIW, that's only their recommendation for dealing with parasites. They recommend 1500+ for bacteria/algae, so perhaps the lower flow is for fish only tanks.

The parasite rating is a fresh water rating and would also be suitable for a fish only marine tank but overkill. It's not appropriate for a reef tank. Once upon a time when Emperor was owned support by Emperor Aquatics, their recommendations were completely different than what Pentair is suggesting today. Unfortunately, the support techs there are ill informed when it comes to UV on marine aquariums. Especially reefs. As I said earlier, 90,000 will deal with parasites. Then again, you will never control marine ich with a UV. You may reduce the populations when it's in the free floating stages but it won't really help regardless of the flow rate. The parasite ends up in the substrate and or find their way back to a host long before any reasonable amount of them will be killed by the UV sterilizer.

 

[earwicker7]

I want it mostly for water clarification, but it would be nice to have some parasite killing capabilities if I need it in a pinch.

 

[HippieSmell]

AFAIK, UV damage is cumulative, so I'm not sure how much difference there is between low and high flow in a small closed system. One of the articles I read showed no decrease in water column bacterial counts between systems running and not running UV. The only article I've seen about higher organisms, such as ich, concluded that you can't ever eradicate anything from a closed system using UV. So, I think it's much easier to have too small a sterilizer than too large.

 

[earwicker7]

We are going to get a slightly larger pump so that I can hit the manufacturer recommended flow.

 

[earwicker7]

AFAIK, UV damage is cumulative, so I'm not sure how much difference there is between low and high flow in a small closed system. One of the articles I read showed no decrease in water column bacterial counts between systems running and not running UV. The only article I've seen about higher organisms, such as ich, concluded that you can't ever eradicate anything from a closed system using UV. So, I think it's much easier to have too small a sterilizer than too large.

This one is designed for around 150g more than my system... I have never heard anyone say going too big was a problem

 

[HippieSmell]

This one is designed for around 150g more than my system... I have never heard anyone say going too big was a problem

Didn't slief feel it's too big? Maybe he just had an issue with the flow rate. But, like I said, I'm not sure there's a big difference between flow rates on small closed systems.

 

[slief]

Didn't slief feel it's too big? Maybe he just had an issue with the flow rate. But, like I said, I'm not sure there's a big difference between flow rates on small closed systems.

Flow rate was my concern, not size. As for bacterial counts, the important (denitrifying) bacteria that we are mostly concerned about colonizes in substrate and within the rocks. As such, UV filters aren't a real concern for that regardless of flows. Waterborn bacteria such as cyano and other waterborn bacteria that more nuisance than benificial will be impacted by UV which is a good thing. My biggest concern is that having too low a flow rate will impact and ultimately diminish pod populations as well as planktonic life over time and as such, we need to be cognizant of that and not run too low a flow rate. Especially considering that targeting parasite such as ich is pretty much an effort in futility with UV filtration in our tanks. Short of running it between systems where you might have a quarantine system plumbed directly to your main system, there really is no justifiable reason to go with excessively low flow rates that put you at 90,000 µw/cm + as you will be potentially doing more harm to the ecosystem than good.

 

[earwicker7]

Flow rate was my concern, not size. As for bacterial counts, the important (denitrifying) bacteria that we are mostly concerned about colonizes in substrate and within the rocks. As such, UV filters aren't a real concern for that regardless of flows. Waterborn bacteria such as cyano and other waterborn bacteria that more nuisance than benificial will be impacted by UV which is a good thing. My biggest concern is that having too low a flow rate will impact and ultimately diminish pod populations as well as planktonic life over time and as such, we need to be cognizant of that and not run too low a flow rate. Especially considering that targeting parasite such as ich is pretty much an effort in futility with UV filtration in our tanks. Short of running it between systems where you might have a quarantine system plumbed directly to your main system, there really is no justifiable reason to go with excessively low flow rates that put you at 90,000 µw/cm + as you will be potentially doing more harm to the ecosystem than good.

 

[earwicker7]

Don't know why that last post didn't include my response...

We're on the same page... I only want to get the bad stuff out, so a bigger pump is being ordered.

 

[ca1ore]

Much ado about nothing IMO. You'd be fine running at 1,300, or even lower than that. Water-borne planktonic populations in our tanks are largely irrelevant anyhow, and I have never seen any correlation to substrate dwelling pod populations and running a UV.