Reef nutrition

UV sizing help needed

What size Aqua UV sterilizer should I get for my 70g tank for general algae and bacteria purposes?

  • 15 watt is all you need

    Votes: 0 0.0%

  • Total voters
    3
I keep going back and forth on this, and only want to buy this once so I could use some help on making a decision.

My tank DT volume is 70g and Sump is 30g. I think it is fair to say total volume after rock and equipment displacement to be 70g give or take.
The UV sterilizer brand I plan on going with is Aqua Ultraviolet and I was deciding between the 15 watt or 25 watt classic.
According to their ratings, the 15 watt version is for tanks up to 75 gallons, while the 25 watt version is for tanks up to 150 gallons.

Based on ratings along I would think 15 watt is sufficient for my tank but I keep second guessing due to these factors:
1. What if my water volume estimate is off? If somehow my water volume turns out to be 80g, would it mean that 15 watts is undersized?
2. Suggested flow rates are 233gph for the 15 watt and 400gph for the 25 watt. My return flow rate is 630gph. Would that mean that I
would have insufficient contact time for both (more so for the 15 watt) if I decide not to adjust that return flow rate?
3. If it turns out that 15 watts is sufficient, would 25 watt be overkill or even potentially harmful to the tank? Or is this a case of more is better?
(or specifically if more wattage compensates for less contact time)

Other factors:
1. Cost consideration: Though not terribly expensive, the 25 watt version costs $77 more than the 15 watt version, so if the extra wattage isn't
needed or helpful then I'd prefer not to waste money.
2. Size consideration: 25 watt version is considerably larger than the 15 watt version and my stand is only 3' by 2'. It'll technically fit in my tank
but the larger one might make the space more cramped and make it potentially harder to work on things in the sump.

Appreciate any input on this. Thanks.
 
I don’t think you will overdo it. Bigger probably better, not sure it’s a must tho.
I would do a manifold off return or use a seperate pump. Flow rate is important.
 
I don’t think you will overdo it. Bigger probably better, not sure it’s a must tho.
I would do a manifold off return or use a seperate pump. Flow rate is important.

So then if I do a manifold, I need to turn down my return pump speed to 400gph right? That would change my tank to sump turnover rate from 9x to 5x. Any concern there?


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What is it for?

Opinion:
If it is for slightly improved water clarity, meaning killing free floating algae only, 15W is probably ok.
If you want to do that plus kill some pathogens, 25W is definitely better, and perhaps small.

Alternative: Split your return into two pipes, so 315 gph each way, and run just one side through UV.
It reduces how much water is treated, but you get better dwell time, which is more critical.
 
What is it for?

Opinion:
If it is for slightly improved water clarity, meaning killing free floating algae only, 15W is probably ok.
If you want to do that plus kill some pathogens, 25W is definitely better, and perhaps small.

Alternative: Split your return into two pipes, so 315 gph each way, and run just one side through UV.
It reduces how much water is treated, but you get better dwell time, which is more critical.
THis is more what I meant by manifold. You can even reconnect them again if you want.
 
It’s for free floating algae and bacteria... protozoas and pathogens are not my main focus. What you and Mike described sounds good, sadly I’m a reef plumbing noob so I’m not exactly sure how to execute those ideas. If there’re are some videos or helpful tips on plumbing a uv I would appreciate the links. (Tried looking it up myself and information regarding plumbing install for uv sterilizers is surprisingly limited)


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Nice! Mind sharing a pic of how you plumbed it?

I went about it like this. I almost cut into the return line to plumb it but decided not to. Instead, went with its own pump.

UV Squist 25W .png
 
Nicely done! Looks like its a tight squeeze to get that skimmer cup out. Do you notice a difference after running UV?

Thanks. It's a rough but simple install, supported by velcro straps; which is good because it's easy to pull out to inspect and clean; see this mistake I made most likely rendering the UV useless for several months. The prior photo showed just 1/2 of the cabinet. There's room to get to the back of the sump and skimmer. It's tight. And as big as I'd go for my set-up, despite @Bruce Spiegelman 's encouragement : )

Hard to tell what difference it's made. My tank was just 6-8 months in when I added it and a lot of other new-tank stuff going on. I installed this to combat dinoflagellates. I can't credit a single factor, most likely it's a combination of factors that clicked, but dinos are no longer proliferating. Will I remove it? Nope. It's staying. Everything is looking good, knock on wood. (Everything except for the mess in the cabinet.)

Another UV pic Squists RSR250.png


Has UV helped dino removal? In some way but not solely, most likely.

Dino update 3-weeks.png

(Many BAR threads on dinos for anyone who finds this and interested in UV and dinos.)
 
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