UV Sterilizer

[svreef]

I got an Aqua Ultraviolet 57W sterilizer for our new tank and I'm starting to think it is oversized. The manufacturer recommends a flow rate of >= 2,100 GPH to achieve 45,000 µw/cm². They say that this "is ideal for the reef environment. UV’s rated at higher kill rates will destroy the planktonic food supply for the reef." They also claim that their units are designed to be plumbed in line with the return - as opposed to bypassing some of the return water. My return pump's maximum rated flow is 2,500 GPH.

So...do I keep this unit and plumb it in line, while running the return pump at 100%?

Do I return it and get a smaller unit? (Their 25W unit wants >= 800 GPH)

Or, do I get a more powerful return pump?

For reference: https://aquaultraviolet.com/wp-cont...s-Classic-and-Twist-Series-02-11-2020-Web.pdf

 

[Coral reefer]

Don’t over think it. That should be a good unit for your tank. What is your main goal for it to achieve?

 

[scuzy]

You want slower flow rate for more contact time to kill stuff. Unless you want to polish your water. I usually t off the return for the uv. I don’t know about having it inline. I guess if you want to achieve 100% kill rate for returning water then plumb it inline and slow the return rate way down.


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[RandyC]

See this thread for previous discussion. Starting around post #28. FYI, I have an AquaUV 57W in an 80-90G system by total volume running around 115gph because I keep forgetting to buy a bigger pump (not installed inline). Things seem to survive plenty fine.

Tank Journal - No Tank

Just wondering, why would it be bad to put even less gph through the UV Sterilizer than suggested by the manufacturer? Is there a negative to UV sterilizer's working too well? I know the debate out there seems to be that they are un-necessary because they usually don't give a long enough...

www.bareefers.org

 

[nly04]

In case if you want to down grade, I have an 25w aquaUV that I can trade.

 

[JVU]

The key difference between what you are reading different places is whether you are going for water clarification (kill bacteria) or sterilization (kill protozoa/parasites). Neither will kill larger critters like amphipods/copepods. The numbers you are quoting from the manual are for clarification. Most of us (myself included) are going for sterilization, as a form of safety net to give our fish a helping hand if they are exposed to any diseases.

If you want clarification (ie no major fish health benefits), then the parameters are very forgiving, and it honestly doesn’t matter nearly as much, you can use the UV unit you have at your return flow rate for example.

For sterilization, not everyone agrees on correct parameters. There are lots of somewhat conflicting numbers out there, but I think the following is useful for sterilization:
8-12 gph/watt
1.5x tank turnover per hour minimum, 3.0x better

So for your tank (like 170g total right?)- 3x turnover is 510 gph, divided by 10 gph/watt gives 51 watts.
So I’d say your size sterilizer is perfect, but you’ll need to plumb it separate from the main return to slow down the flow rate to around 500 gph.
Or you could slow your return pump way down and plumb in-line. Lower sump turnover rates are more fashionable lately anyway.

Just remember that your return flow rate will be much less than what it is rated for, so you should just measure it. If you have a flow meter, great. If not, plumb everything the way it’s going to be, then time how long it takes to fill a 1g or 5g bucket from the return nozzle at different settings, and do the math.

I have a 55w UV sterilizer on my RSR 750 (just a smidge larger than yours), not plumbed into my return but separate in my sump, FWIW.

 

[svreef]

I guess my concern is that too low of a flow rate will kill the pods’ food.

My 55g was infested with ich and the UV did an incredible job getting it under control.

My gut tells me to plumb it in-line and try to maintain close to 2,000 gph through it, which is the manufacturer’s recommendation and also the 10x turnover recommended by Red Sea. It also keeps things simple.

 

[RandyC]

I guess my concern is that too low of a flow rate will kill the pods’ food.

My 55g was infested with ich and the UV did an incredible job getting it under control.

My gut tells me to plumb it in-line and try to maintain close to 2,000 gph through it, which is the manufacturer’s recommendation and also the 10x turnover recommended by Red Sea. It also keeps things simple.

2000gph will mostly function as a clarifier. It will do nothing to help manage larger parasites like ich.

 

[Squist]

I was concerned about low flow too, though less after seeing significant increase in my tank's biodiversity since adding the UV Feb 2. I am running 1/2 the manufacturer's recommended flow on a 65g tank running a 25w UV.

Using John's sizing formula, for my 250 liter (~65g):

65g x 3x turnover is ~200 gph, divided by 10gph/watt = 20W. I'm running a 25W. Check!​

While the manufacturer for this size UV is recommending a flow of 1200-800gph for 30K-45K µW/cm^2 (Aqua Ultraviolet's recommendation for a reef tank), I am running it a 500 gph. It's the most my 1000 gph pump will move through the fittings and sterilizer at < 1' head. Measured with a flow meter, it clocks at 500 gph. I have this running apart from my return, in a loop, in my sump. Except for a few hours after dosing Microbacter7 (providing a bio-boost), it runs 24x7.

I'm using UV to address dinos. Given my tank is new (10 mos.) and the dino issue was caused, I believe, by sterile conditions, I was concerned I'd be killing-off micro organisms. I'm not seeing that to be the case. I've been taking photos of my sand bed using a USB magnifying scope. I see a significant increase in organisms in the sand bed over the last couple months. And, using the scope just viewing the water column, I see amazing comet-like streaks of life in the water. I have no idea what these bugs are. They appear to be white in light, move super-fast, and pivot on a dime. Anyone know what are these are?

https://imgur.com/a/rHpJbwM

 

[svreef]

Very useful information.

@Squist - how often do you dose bacteria? Do you think that’s necessary because the UV is killing too much of it?

 

[Squist]

I'm dosing bacteria because I believe my tank was sterile. It was my first time kicking off a tank using dry rock and cycling from a bottle. On top of it all, I was doing auto water changes post-cycle thinking I could get on top of ugly-tank syndrome. Maybe not even have it happen. In the end, I did more harm than good. Lack of biodiversity, from what I have researched, experiences others have shared, and feedback I've received, suggest I created a perfect environment for dinoflagellates to thrive. I have a tank journal where others are discussing this with me; an update soon after I get ICP test results back, though it most likely delayed given circumstances.

I don't think UV is killing too much bacteria -- but I will continue to dose bacteria even after my initial high-level dosing phase through this month.

 

[Coral reefer]

It will only kill free floating stuff in the water column. I wouldn’t worry about bacteria getting killed too much. It mostly lives on rocks and substrate.
There will likely be plenty of detritus and micro algae on rocks and such to feed pods. I wouldn’t worry about free floating plankton.

 

[svreef]

Thank you all. It feels really good to have your knowledge and experience at my fingertips.

 

[svreef]

Ok so I decided on a second pump dedicated to the uv which I’ll
place in the return area. Question is, what sump compartment should the uv drain into? Draining into the return area seems like a good option to maintain water level

 

[Squist]

It's a closed loop, essentially. Not sure it matters. For my set-up, I went wherever the sterilizer fit best. I am drawing water into sterilizer from the compartment after the sump's pre-filter and returning the water back into the pre-filter area. A short reverse loop at 500 gph.

 

[JVU]

In my tank I have both intake and output in the same compartment, my skimmer/probe/reactor/heater compartment. Intake on the side farthest from return chamber, output closest to the return chamber. I could have put output in the return chamber, but I was worried that it could partially bypass and lower my skimmer etc chamber which I like to keep at a constant level with constant flow.

 

[rygh]

If you are going with a second pump, why not have dual returns?
Having that redundancy adds a big safety factor, since pumps can fail.

 

[svreef]

It just complicates the plumbing. This way, if the return pump fails I can switch it out with the uv pump until I replace it.

 

[scuzy]

Why not just use one pump to drive everything. If it fails then replace why worry? If you got a quality return pump it won’t fail on you like the crappier ones.


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[Squist]

Same here: it was easier for me just to put it in the sump independent of everything else. And I’m working with a small system, so not much room

I’ve wondered about improved performance setting it up as closed loop directly in the display. I’m guessing there might have been faster initial improvement but over long term, same.

Here’s a pic:

The pump is rated at 1000 gph. It cycles at 500 gph, given plumbing down-steps.

Side note: the red silicon ice cube tray from Bed, Bath, Beyond does a great job dampening pump vibration.