UV Sizing help

[BAMatter]

Hi everyone, or whoever reads this at least. I’d like to purchase a UV for my system. It’s a 75 gallon display with a 34” Trigger Systems sump that I’m estimating to hold around 20 gallons. Looking at the Aqua UV- my question/inquiry is this- they claim:

8 watt up to 70 gallons
15 watt up to 75 gallons
25 watt up to 150 gallons

With the substantial jump in gallonage from 15 to 25 watt, looking backwards why would the 15 watt only be a 5 gallon increase over its 8 watt counterpart? Would the 15 watt unit be ok for my system, the dimensions are a concern on this, it’s a bit tight under my stand.

Thanks!

 

[Quietman]

Just looking at watts leaves a lot out. UV sizing is based on controlling two types of issues each requiring a different exposure and tank turnover rate. For algae/dino an exposure of at least 30000 uw/cm2 is required. But that's at a turnover of around 8x true tank turnover per hour (not flow rate) as some species can double population every 20 min. Pathogens (ich/velvet) need at least 90000 uw/cm2 on up to 180000 uw/cm2 for most. Turnover can be much lower.

So one, make sure vendor you choose provides exposure rates for a given flow. It's proportional so you can figure out different exposures at different flows easy.

Two decide size of UV based on which organisms you want protection for and for both you'll need larger UV for constant flow or smaller UV and variable flow.

Three. Decide how you want to pipe it into system. Picking right size and plumbing it in sump supply and return isn't going to as effective as plumbing in return or a closed loop to/from display.

 

[Saltysav96]

im glad i came across this because i have been wondering the same.

i have been under the impression i needed a 25 watt UV for my reefer 525.

a good friend of mine told me the aquatop 13watt UV would do the job.
the aquatop UV Is rated 125-150 gallons, so i picked one up since it was cheap and could be ran internal. figured it was better then not having one at all.
i cant say i actually see any difference running this 13watt UV on my system...
BUT the aquaUV 25 watt Is rated for 150 gallons.

thats a big jump between 13-25 watts so i am definitely confused with the whole wattage to tank size thing.

 

[BAMatter]

Just looking at watts leaves a lot out. UV sizing is based on controlling two types of issues each requiring a different exposure and tank turnover rate. For algae/dino an exposure of at least 30000 uw/cm2 is required. But that's at a turnover of around 8x true tank turnover per hour (not flow rate) as some species can double population every 20 min. Pathogens (ich/velvet) need at least 90000 uw/cm2 on up to 180000 uw/cm2 for most. Turnover can be much lower.

So one, make sure vendor you choose provides exposure rates for a given flow. It's proportional so you can figure out different exposures at different flows easy.

Two decide size of UV based on which organisms you want protection for and for both you'll need larger UV for constant flow or smaller UV and variable flow.

Here are the specs on the 2 in question. A 25 watt and a 15 watt. I’d like to purchase the 15 watt, more for disease control than algae control. I’m just at the cusp of sizing between the 2. I “think” I’d be ok with the 15 watt, especially given the large jump between the 15 and 25 watt units, and also considering the 8 watt is rated at 70 gallons. I just don’t get the math/reasoning behind those figures.

 

[BAMatter]

im glad i came across this because i have been wondering the same.

i have been under the impression i needed a 25 watt UV for my reefer 525.

a good friend of mine told me the aquatop 13watt UV would do the job.
the aquatop UV Is rated 125-150 gallons, so i picked one up since it was cheap and could be ran internal. figured it was better then not having one at all.
i cant say i actually see any difference running this 13watt UV on my system...
BUT the aquaUV 25 watt Is rated for 150 gallons.

thats a big jump between 13-25 watts so i am definitely confused with the whole wattage to tank size thing.

Are you looking to control algae or parasites? I think that’s the main factor here, I just have no idea if I can get away with the 15 watt, but I’m hoping I can

 

[Saltysav96]

Honestly both. but more parasites then anything. i can control algae with other means

 

[BAMatter]

Are you looking to control algae or parasites? I think that’s the main factor here, I just have no idea if I can get away with the 15 watt, but I’m hoping I can

I gotcha. Yea only reason I was wondering was because of different flow rates for different purposes. Wondering how that takes into account what size to get.

 

[Quietman]

Here's the flow/exposure/size chart from AquaUV.

For 15W, you need to have 700 gph through the UV to provide 30,000 uw/cm2 (again, it's not primarily the wattage but the exposure the wattage can provide). Your tank is 75 gallons, that would mean you would need 600 gph tank turnover to protect against algae/dinos (and yeah, you say it's just disease, but wait until you get dinos). So you're good there assuming you have it plumbed.

For pathogens, the chart says 90,000 mw/cm2 (and that's bare min) is 233 gph. So as long as you have adjustable speed pump the 15 watt will work.

However, if you want constant protection/coverage against both you would actually need the 40 watt which will give 90,000 uw/cm2 at 967 gph - and your flow of 600 gph for turnover would cover you on both. But if you're starting out, that's a lot of dollars.
Get the 15 watt with a dc pump that has adjustable flow. Just realize if you see symptoms of algae/dino you may have to increase flow and if you see ich you might have to decrease.

 

[BAMatter]

Here's the flow/exposure/size chart from AquaUV.

For 15W, you need to have 700 gph through the UV to provide 30,000 uw/cm2 (again, it's not primarily the wattage but the exposure the wattage can provide). Your tank is 75 gallons, that would mean you would need 600 gph tank turnover to protect against algae/dinos (and yeah, you say it's just disease, but wait until you get dinos). So you're good there assuming you have it plumbed.

For pathogens, the chart says 90,000 mw/cm2 (and that's bare min) is 233 gph. So as long as you have adjustable speed pump the 15 watt will work.

However, if you want constant protection/coverage against both you would actually need the 40 watt which will give 90,000 uw/cm2 at 967 gph - and your flow of 600 gph for turnover would cover you on both. But if you're starting out, that's a lot of dollars.
Get the 15 watt with a dc pump that has adjustable flow. Just realize if you see symptoms of algae/dino you may have to increase flow and if you see ich you might have to decrease.

I was more concerned with gallonage of sump added to display size as well pushing me over the rating. Thanks for the input, I’m still leaning towards the 15 watt, it will be hard plumbed in with a gate valve to control flow.

 

[Quietman]

So if I were limited to an AC return pump (as it's a good decision for a lot of reasons) and couldn't adjust flow and needed to be as economical as possible, what I'd do is put the 15 w in the return line with unions/nozzles so you can remove it easily if needed. This will be the lower flow needed for pathogens and do just fine.

If you get a dino outbreak (and I really hope you never do) you could always remove the UV from the return line and drop a higher flow ac pump directly in your display tank and connect the UV with hoses and have the discharge right back in display tank. It's not going to look pretty but if you get a break out it'll be nice to have the option and you won't care about looks if dinos show up.

And if you never need to do that, you still have solid coverage piped inline with return. Plus preventing outbreaks takes less than dealing with them afterwards so you could be just fine forever (change the bulb out annually).

Good luck!

 

[BAMatter]

So if I were limited to an AC return pump (as it's a good decision for a lot of reasons) and couldn't adjust flow and needed to be as economical as possible, what I'd do is put the 15 w in the return line with unions/nozzles so you can remove it easily if needed. This will be the lower flow needed for pathogens and do just fine.

If you get a dino outbreak (and I really hope you never do) you could always remove the UV from the return line and drop a higher flow ac pump directly in your display tank and connect the UV with hoses and have the discharge right back in display tank. It's not going to look pretty but if you get a break out it'll be nice to have the option and you won't care about looks if dinos show up.

And if you never need to do that, you still have solid coverage piped inline with return. Plus preventing outbreaks takes less than dealing with them afterwards so you could be just fine forever (change the bulb out annually).

Good luck!

I will be able to control flow, this pump is a second pump in the system and will be feeding my carbon reactor and UV (none of which is pictured) Will be building a small manifold with 2 outputs both of which will have controllable flow- I’ll just need to fill up a gallon jug and do the math calculation to adjust flow correctly. I have a Sicce 5.0 for my return and will be running a Sicce 3.0 for this manifold. The UV will also be plumbed in with unions for ability to remove or rework the plumbing if needed.

 

[Quietman]

Ah...so be aware. Taking sump flow and returning to sump is going to be much less effective as the sump is only seeing a fraction of the tank (return pump) and the UV pump is taking a portion of that. It'll be very hard if not impossible to get full UV effectiveness with sump manifold plumbing for UV.

If that was my only option, I'd still go with putting in return line over sump manifold (as I have plumbed now actually - I'd prefer closed loop dedicated but that's next tank).

 

[BAMatter]

Ah...so be aware. Taking sump flow and returning to sump is going to be much less effective as the sump is only seeing a fraction of the tank (return pump) and the UV pump is taking a portion of that. It'll be very hard if not impossible to get full UV effectiveness with sump manifold plumbing for UV.

If that was my only option, I'd still go with putting in return line over sump manifold (as I have plumbed now actually - I'd prefer closed loop dedicated but that's next tank).

Thanks for your help!