1 vs 2 UV

[Aardvark1134]

So here is a question:
Lets say you have 1 UV that can do 180,000 uw/s/cm2 @667 gph or 1,333 gph @90,000 uw/s/cm2
Could you just add a 2nd one in series and end up with 1,333 gph @180,000 uw/s/cm2 ?
Basically does running from 1 UV right into another where each is running 1,333 gph @90,000 uw/s/cm2 give you 180,000 uw/s/cm2 or do they not add effectiveness like that? I would think having 2 in series would end up doubling the dwell time.

 

[Aardvark1134]

I know running them in paraelell each with half the flow will work but not real sure how to ensure each one is getting 50% of flow reliably. So if serial will work it seems the plumbing would be much easier.

 

[dwest]

I’m pretty sure you are correct. For example, if you look at the 57 watt vs 114 watt aqua uv unit, there are two 57 watt units in series it appears. I know when I was killing dinos, I ran two smaller units in series that seemed to have a better kill rate than a single unit.

 

[Xero]

Yes, you can definitely chain them together, and this is what many of them amount to.

Trusting those exposure times to actually kill ich is your next mistake. Look up what it actually takes to kill ich in saltwater vs freshwater, most published numbers put you at 300k to 800k, so I really dont know what they are smoking.

That said, the easiest way to increase exposure time is to decrease flow rate. Half the flow rate for 180k, and you get 360k. Generally, you want at least 1x turnover of your tank volume, so that's actually how I size the UV. By dividing that 180k flow rate in half number, find the one which can do 1x your tank volume, per hour. Or in the case of aquaUV, divide their 90k flow rate by 4. I didn't entirely come up with this - it's a combination of information from another forum, and various anecdotal stories.

 

[Aardvark1134]

Where did you get your #s the ones I have seen are:
Killing Dose of UV light*
Bacteria = 15,000
Viruses = 15,000-30,000
Algae = 22,000-30,000
Fungus = 45,000
Chlorine = 90,000
Protozoa = 90,000-180,000
Ich = 100,000
And I was trying to keep turnover at about 3x do you really think 1x would be enough?

 

[Xero]

Where did you get your #s the ones I have seen are:
Killing Dose of UV light*
Bacteria = 15,000
Viruses = 15,000-30,000
Algae = 22,000-30,000
Fungus = 45,000
Chlorine = 90,000
Protozoa = 90,000-180,000
Ich = 100,000
And I was trying to keep turnover at about 3x do you really think 1x would be enough?

Some of my suggestions came from here:
https://atlantareefclub.org/boards/index.php?threads/properly-sizing-uv-sterilizers.15871/

unfortunately, some of those links are dead, archive.org that stuff if need be. There used to be a diagram of actual freshwater protozoa, and freshwater ich took 336,000uw/cm2 by that count. The estimates I've seen for saltwater ich (crypto, really) rate it at anywhere from 300-800k......

For example, this paper here:
https://pearl.plymouth.ac.uk/bitstream/handle/10026.1/2632/PETER JOHN BURGESS.PDF?sequence=1&isAllowed=y

"Spotte (1979) estimated from the size of the theront stage that the minimal lethal dose of U. V. needed to destroy C.irritans would be 800,000 uw/cm2"


I feel like 300k is already being optimistic, and these 90-180k numbers are a borderline joke, based only on freshwater data, if even that. There's also a ton of anecdotal stories/experiences I've heard through my old LFS owner, his service guys, etc. They all match these accounts, which makes me fairly confident (though i'm sure this anecdotal tale isn't quite as helpful to you, lol)

I'm also slightly disappointed that companies like BRS seem so quick to just believe the numbers from these manufacturers as-is in their videos....

 

[Aardvark1134]

Other than ich are there any others that need more than 180K as honestly ich isnt that bad to deal with you usualy see it in time to help the fish. Now if you have to catch all your fish...well that sucks but I haven't seen ich send fish belly up before you even know there is an issue. Like by the time you know something has velvet you are usually trying to save the ones that don't show it yet. Luckly I have never had a main tank get hit with velvet although my QT tank got hit with it once...I bought a new QT tank to make sure it was gone lol

 

[Xero]

Other than ich are there any others that need more than 180K as honestly ich isnt that bad to deal with you usualy see it in time to help the fish. Now if you have to catch all your fish...well that sucks but I haven't seen ich send fish belly up before you even know there is an issue. Like by the time you know something has velvet you are usually trying to save the ones that don't show it yet.

To be frank with you - I don't feel like I have enough unbiased data to fully give an opinion on this. What I can say for sure, I definitely do not trust the numbers from these manufacturers, I'm highly skeptical. Most of these charts end up being freshwater-specific, or specific to certain organisms, but not others. A proper chart in this regard would be quite valuable, but even then, there might be studies with conflicting numbers. It's never so clear cut.

I've had very good luck with sizing them in this way though (targetting around 336k) and I know many others who have as well. That said, you could definitely go all sorts of crazy here, but I think this is a good target to achieve many goals.