The Gray Area of Flow Rates for UV Sterilizers

[fishybizzness]

So i was just wondering if anyone has opinions on the "Gray Area" of recommended flow rates with regards to protozoa vs algae and bacteria control. I am currently running a Pentair 40 watt uv on my 120 dt. I have it running at around a 200 gph flow for crypto/ich control. Pentair recommends a 157-262 gph flow for this purpose. For Algae and bacterial, the flow is of course much higher at 943-1574 gph. If i run the uv at 400-600 gph, will the impact to either protozoa or algae be nonexistent or will it still affect and sterilize both of them, just not in any noticeable way? I've been wondering about this and would like your opinions.

 

[Wayne P.]

I would think that if you are running at the slower rate it will take care of everything. The slower rate is to allow longer contact time with the UV light. That will allow better penetration of the light into the organisms. Meaning if the hard to kill stuff needs the longer contact time then the weaker stuff will be wiped out as well. I would maybe go up to 240 gph as that will give you 2 complete cycles of your water through the UV. Just MHO.

 

[sdreef]

So i was just wondering if anyone has opinions on the "Gray Area" of recommended flow rates with regards to protozoa vs algae and bacteria control. I am currently running a Pentair 40 watt uv on my 120 dt. I have it running at around a 200 gph flow for crypto/ich control. Pentair recommends a 157-262 gph flow for this purpose. For Algae and bacterial, the flow is of course much higher at 943-1574 gph. If i run the uv at 400-600 gph, will the impact to either protozoa or algae be nonexistent or will it still affect and sterilize both of them, just not in any noticeable way? I've been wondering about this and would like your opinions.

My understanding is that it is related to the dosage of UVC that you get that is necessary to kill the organism that your targeting. So if you increase the flow, you may not get sufficient UV damage to eradicate a larger organism like protozoa. If you reduce your flow, you may not pass sufficient volume of water to have a meaningful impact on large number of organisms as in a bacterial bloom or for algae.

For protozoa, the number I have seen to target is 180,000 µW/cm2. Different manufacturers have different targets, and I don't think there is great evidence. So if you are running your flow at a higher rate, and reducing the UVC the organism is exposed to, it may be insufficient to have an effect in theory.

 

[piranhaman00]

Using your example, you have all no impact on protozoa but you will destroy and bacteria or unicellular organisms.

The high flow rate for bacteria is so that you turn more water over. Of course, any flow rate less than the recommended is going to increase the dose of UV and thus be more effective, but since you are turning the water over less, you arent killing as much.

However, I have found that the turn over rate for water clarity and bacterial sterilization can be much lower than recommended. I turn my tank over 3x an hour and its crystal clear. In theory it should need more turn over to kill all free floating micros.

 

[SPR1968]

You really want to run it as slow as you can get away with to intensify the power and also use the most powerful you can fit into your system otherwise they can often be ineffective

Part of the ich life cycle is the free swimming stage and if it passes through a UV-C at high enough power, around 72000 micro watts/sec/sqcm it should kill it. It’s not a cure for ich, it’s a method of ich management. So if you using it for this like myself, I’ve got a very powerful unit and low flow.

I use a DD Professional 80w UV-C which is roughly equivalent to a 160w conventional unit.To be effective you need to know the power rating and then do a bit of maths to achieve the correct flow rate. If you don’t, many hobby grade UV’s are not powerful enough to be effective

It will also kill anything else that passes through it, provided the power is high enough. Thats why you don’t run one when setting up a new tank with bottled bacteria or when adding additional bacteria to a system.

 

[hogger555]

This is a great article about UV. It answered all of my questions and more.

UVC Sterilization | How Aquarium & Pond UV Sterilizers Work

Information how a TRUE Aquarium, Pond UV Sterilizer/clarifier work. Category A, B, & C Sterilizers. Affect on green water, disease prevention, & Redox

www.americanaquariumproducts.com

 

[piranhaman00]

You really want to run it as slow as you can get away with to intensify the power and also use the most powerful you can fit into your system otherwise they can often be ineffective

Part of the ich life cycle is the free swimming stage and if it passes through a UV-C at high enough power, around 72000 micro watts/sec/sqcm it should kill it. It’s not a cure for ich, it’s a method of ich management. So if you using it for this like myself, I’ve got a very powerful unit and low flow.

I use a DD Professional 80w UV-C which is roughly equivalent to a 160w conventional unit.To be effective you need to know the power rating and then do a bit of maths to achieve the correct flow rate. If you don’t, many hobby grade UV’s are not powerful enough to be effective

It will also kill anything else that passes through it, provided the power is high enough. Thats why you don’t run one when setting up a new tank with bottled bacteria or when adding additional bacteria to a system.

Yes but this information only applies to parasites. OP doesnt really state what they want to use it for.

For instance, I dont use my UV for ich, I use it for bacteria and clarity. I run lots of water through my unit and I dont want to slow it down at all.

 

[SPR1968]

Yes but this information only applies to parasites. OP doesnt really state what they want to use it for.

For instance, I dont use my UV for ich, I use it for bacteria and clarity. I run lots of water through my unit and I dont want to slow it down at all.

That’s fine, you can run them at whatever rates you need to achieve your goals, all systems are different and if it’s just clarity of course as you say, you can run higher flow rates

Personally I run mine 24/7 as a ‘killing machine’ for everything that goes through it and then I don’t need to worry about flow rates, I’m covering all angles.

It’s on 24/7 365 and I just change the bulb every 12 months.

 

[fishybizzness]

I am currently running it at 200 gph for ich management. I don't think i would ever run a tank without a uv. The reason for this is that as shown in some of my early threads, i went through a lot of issues keeping fish alive for more than a few weeks at a time. I work long hours so even thinking about setting up a quarantine system would be a waste of time as my schedule fluctuates too much for me to ever stick to it and be successful. After doing research, i ended up adding a uv and the effect was drastic. I also feed fresh homemade food and gridal worms as per advice from Paul B. I may still see a few spots now and then but they usually go away after a few days. Ive lost a fish or 2 since but due to bullying or carpet surfing. I am a firm believer in the powers of uv. I was just curious as to if anyone feels there are any benefits or negative impacts from running in the flow rates between the recommended high end of the flow rate recommended for parasites and the low end of the flow rate recommended for algae. I just figured it would be a good topic for conversation and debate and it is definitely turning out to be. Thanks for the responses and keep them coming!

 

[Devaji]

I have the same UV on my up and coming red sea reefer 650P. I am often wondered the same.
I "think" it would be best if we could run 2 units. one for keeping tank nice and clean the other of protozoa...BUT these things are expensive and HUGE just think of plumbing in 2 units...ummm no thanks I cant even fit the 40W in my sump area...

I have struggled ( in my brain ) as to what flow rate i should set it at. one would think that slower flow rates for protozoa would also help with algae, to what level I have know idea.
but then again that stuff multiplies fast ( I believe) that is why we need high turn over rates.

I am with you there would seems to be a sweet spot to help with both. maybe someone will do more research?

another option and I'll admit it may not work. would be to use the pentair for the protozoa and get a cheap smaller unit just for the algae.

 

[Devaji]

on a side note I wish someone would come out with smaller more powerful units stacked together that could be controlled independent of each other with build in flow meters so you could get both benefits at optimal UV-C contact time for best in tank perfermance.

#milliondollaridea

 

[Saltyanimals]

Interesting. I too was after some magical sweet spot for both algae and bug zapping. Like others that posted here, I assume going as slow as possible will kill everything through the powerful tube.. so why wouldn't it kill algae as well. Yes slower and may not turn over the water fast enough....but is it really a race to turn water over fast? "Eventually" wouldn't all the water pass through the UV at some point and there you have bug free + algae free?

I'm personally putting 125gph through a 57w which gives me probably 200k+ µW/cm2 will eventually kill everything.

I make sure I don't stand in front of the UV myself too long so it doesn't sterilize me.

 

[fishybizzness]

The pentair uv is one of the companies with the most precise flow rate recommendations for specific purposes that I've seen. I have been wondering about the flow rates between the 2 specific uses which is why I started this thread. I was just wondering what everyone's thoughts were on this topic and so far it has definitely been interesting and informative!

 

[DxMarinefish]

Fantastic topic. I have just bought myself the DD Professional 80w UV-C and will be running it with a sweet spot for both 2 specific uses. I think I will be following @SPR1968 method and see how it goes.
My system is roughly 1000 litres with displacement.

Just need to calculate what the "sweet spot" flow rate will be. I rune 2x powerful ATS and sometimes I do get a little bit of yellowing. I just use Seachem Purigen when this happens but it can be a pain to fluidise for maximum effect.

I figure with the UV i can achieve both 2 specific uses.

It's good to Experiment.

 

[Saltyanimals]

I think the sweet spot may be possible, but probably not effective in terms of targeted purpose since the flows are dramatically different.

I've personally abandoned finding the sweet spot, but instead will depend on a quality gate valve (not ball) to control flow speed + a flow sensor to read. This allows you to select purpose based on your immediate need. i.e . bug zap when adding new animals or algae when you're starting to see something you want to get ahead of using a single device.

 

[Dj City]

Here's the answer that is correct but you won't want to hear.

There is no grey area. There is no sweet spot.

It's one or the other or neither.
UV MUST be properly sized to the tank.
UV MUST be properly plumbed and it MUST have the correct flow for what you are targeting.
If you miss any of those three requirements, your UV will not work.

For ich and the like, you need the slow flow that is stated by Prntar. It is not a recommendation, It is a requirement. Faster flow will NOT work.

For algae and the like, you need the faster flow that is stated by Pentair. It is not a recommendation, it is a requirement. Slower flow will NOT work.

Slower flow will kill the algae but algae will reproduce and spread faster than the slow flow can handle. The UV will never be able to knock it down with the flow slower than stated and required.

The faster flow for algae will not harm the ich because there is not enough dwell time.

Sorry to be the bearer of bad or unwanted news but the fact is...

There is no sweet spot.

 

[Malcontent]

What happens to ich that doesn't receive a lethal dose?

 

[takitaj]

The flow rates are based on the UV dosage depending on the power of the bulb. For example an 18 watt wants say 250 gph to give the dose to affect a protozoan. A 40 watt can give the correct dosage at say 900 gph.

The reason to run a higher flow for algae & bacteria is to beat out the reproduction rate. So if you use a large enough UV the protozoan flow rate is high enough to be able to keep up with bacterial and algae reproduction rates. So no real gray area but you can size it to be able to pull double duty.

For example I run a 40 watt Pentair at about 800 gph (spec'd for 7-900 gph for protozoan) on my 90 which meets the protozoan rate but gives me almost 9x per hour turn over to keep up with reproduction rates.

 

[Dj City]

What happens to ich that doesn't receive a lethal dose?

They never receive a lethal dose.
What happens is that the UV alters (destroys) their ability to reproduce. It can kill some but it leaves them sterile. (UV STERILIZER)

Not enough dwell time and they will simply enjoy the pretty violet colored light and continue on with their lives.

 

[fishybizzness]

What i like most about starting a thread is all the great perspectives and valuable information we all get from all the members willing to take the time to explain different aspects of the hobby! This community is really an awesome place to be a part of!