Is UV actually viable for parasite management?

[allenk4]

You are free to hold any opinion you wish, but what you just said is simply not true. Nobody here is protected from disagreement, me, Randy, the ownership, staff or you. You are free to, and openly encouraged to debate your point as long as you do so within the confines of the TOS.


You pulled "nearly" and "less" out of a sentence that listed rock, varied flow patterns, striations, eddies, and nearly dead zones. The purpose of the whole list was to describe non-uniform flow. You dropped the context, swapped in "zero," to change the meaning.

Fact and the point: Some areas run below the tank average, and that alone breaks the equal probability assumption your n-passes math requires. You used the wrong model to argue. Full stop.

Also: The differential pressure article you quoted and cited is about pressure drop across industrial filter media. Zero crossover to tank mixing and zero relevance to any argument here, and the line you quoted isn't in it. Was that citation AI Search derived?


I very clearly laid out that your model assumes a single dose of something that can be traced as mixed into the water, not that UV is a single dose. I also clearly laid out that the target itself, parasite, bacteria, or anything else living in the water, is not a single dose, but a series of "doses" as the population expands.

UV doses accumulating was never the argument. The argument is that the calculator you used to make your case doesn't model any of this. Clearly laid in my original post and here.


I said flow moved detritus there, so flow exists there. Reduced flow is what a low-flow zone is. You are confirming my point and calling it a rebuttal.

Note: second time you have misstated what was said. I said non-uniform flow, some areas below the tank average. That is what breaks your equal-probability assumption. It does not require zero.

Telling me to fix my low-flow zones doesn't answer the argument or make yours. Every tank with rock in it has flow variance. It's the reason the uniform mixing model doesn't apply, not a defect in plumbing.


Randy already corrected this. Even in an ideal model with no obstacles and perfect decay math, the number does not reach 100%.

You then cited a calculator that proves him right. It returns 99.9%, not 100%. It never gets there. That is the stirred tank problem. You agreed with Randy in theory, posted the tool that confirms him, and then wrote that "there is no doubt 100% of the water molecules circulate through every powerhead and pump". That is contradictory on its face.

And if your position is that 98%, 99.9%, and 100% are close enough for practical purposes, that dismantles the absolute claim you just made. Your arguments are running into each other.

Randy's point stands in the ideal case. In a real tank with rock, the ideal model does not apply at all, so 99.x% goes out the window too.

Second, and much more important. Water molecules aren't the argument anyway. Theronts (the example you used) are not water molecules. They swim, they respond to flow and light, they concentrate in some zones and avoid others. Sessile stages are attached to surfaces and don't move at all. None of that is evenly distributed, and I said so already. No simple mathematical regression or decay model can account for this in an ideal aquarium, let alone a real one with fish, disease, substrate, rock, and everything else in the way.

Not everything in the water goes through the pumps. Period.


My response has nothing to do with UV being effective or not. I am responding to your claims and arguments about flow. That's all.

You brought detritus into this as your own evidence, and I pointed out it works against you.

So we are arguing over .1% ?

 

[sixty_reefer]

That statement is certainly untrue. No pun intended, disagreement is the life blood of the scientific method and is not frowned upon at all (assuming it is polite and respectful per the TOS).

I’m not sure that’s true either.

 

[sixty_reefer]

I’ll just make one comment here. In any tank system, not all water passes through the filter system. It’s a classic problem in math called the stirred tank.

If one is adding and removing water from a stirred tank (like a reef aquarium), there is always some water and its contents that is never removed. In this context, that means some never passes through the UV.

Does that matter for using a UV? Probably not, but I wanted to address the assertion made above that 100% of tank water passes through it.

I don’t think the stirred tank analogy fits this particular discussion. The classic stirred tank model describes the replacement of water that’s continuously entering and leaving a vessel. In that scenario, the fraction of the original water approaches zero asymptotically and never reaches exactly zero in finite time.

A reef aquarium with a UV is a different system. It’s a closed, recirculating loop where the same water is continuously mixed and recirculated rather than replaced. The question isn’t whether 100% of the original water has been replaced, it’s whether water eventually passes through the UV. Those are different problems.

The stirred tank model doesn’t demonstrate that some water can never reach the UV. It describes replacement kinetics, not permanent exclusion from circulation. In a functioning aquarium, water is continually exchanged between high and low flow regions, so while some areas may take longer to reach the UV than others, that’s not the same as showing they never do.

 

[BeanAnimal]

So we are arguing over .1% ?

No, not correct and citing any number would misrepresent what happened.

We are not arguing over 0.1%. That number came from a model that does not apply to an aquarium. There is no number here. What we do know factually is that the model you used cannot produce it.

You stated 100% of the water molecules circulate through every powerhead and pump, no doubt. Randy corrected that. Your own cited calculator reference returned 99.9%, which contradicts that claim, but it doesn’t end there.

The calculator assumes a single fixed quantity added at time zero and instantaneous, uniform mixing: where whatever re-enters from the pump (filter) on each pass is distributed evenly through the whole volume immediately, and every unit of tank volume has equal probability of being drawn out on the next pass. A reef tank has rock, varied flow, and a reproducing target population. None of it fits the calculator cited.

And theronts are not water molecules. They swim, they respond to stimuli, and are not evenly distributed. A water mixing calculator can’t tell you what fraction of them passes through the UV chamber.

The rest of it, the either/or flow argument you set up, the article you linked, all wrong. There is no 0.1% to argue over because there is no number or fraction to split.

In the real world the problem is complex because every aquarium is different. Different structures, non-uniform flow paths, often with multiple pumps, sumps, skimmers, reactors and other devices that don’t just break the uniform mixing model, they turn it on its head, and that is still outright ignoring the target organisms that are motile, not homogenous with the water.

None of this is to say that UVs can’t be effective at some size and turnover rate. The argument was against your framing of it as a simple n-turns calculation and the absolute and incorrect claims used to support it.

 

[BeanAnimal]

I don’t think the stirred tank analogy fits this particular discussion. The classic stirred tank model describes the replacement of water that’s continuously entering and leaving a vessel. In that scenario, the fraction of the original water approaches zero asymptotically and never reaches exactly zero in finite time.

You're attributing an argument to Randy that he didn't make and answering something that wasn’t said.

His simple point wasn't that the stirred-tank model perfectly describes an aquarium. It was that even assuming the ideal mixing model AllenK4's claim doesn’t hold.

 

[sixty_reefer]

You're attributing an argument to Randy that he didn't make and answering something that wasn’t said.

His simple point wasn't that the stirred-tank model perfectly describes an aquarium. It was that even assuming the ideal mixing model AllenK4's claim doesn’t hold.

If you don’t mind, I’d prefer to hear it from the person I quoted, since it’s their statement I’m trying to understand.

 

[BeanAnimal]

If you don’t mind, I’d prefer to hear it from the person I quoted, since it’s their statement I’m trying to understand.

That is not how this works. This is a public thread on a public forum. Anybody here is free and encouraged to add context or respond, that's how forums work. So yes, I do mind.

Randy's point was narrow: even in an idealized model, not all water passes through the UV. That's already answered above, in his own words.

 

[sixty_reefer]

That is not how this works. This is a public thread on a public forum. Anybody here is free and encouraged to add context or respond, that's how forums work. So yes, I do mind.

Randy's point was narrow: even in an idealized model, not all water passes through the UV. That's already answered above, in his own words.

In that case, could you point me to the evidence that, in a closed recirculating aquarium, some water never passes through the UV? I’m asking specifically about that conclusion, not the stirred tank mathematics itself.

 

[Freenow54]

How is this even a question or debate at this point?

Is the sun actually a viable way for getting a sunburn???

Chime in instead of criticizing seriously what you said adds nothing so add something

 

[Freenow54]

The UV debate is almost political in nature because it is tied to broader, deeply held philosophies: natural methods versus reliance on technology versus zoological-level eradication. These philosophies tend to dictate a wide array of beliefs.

Outside of that. Imagine how much crow any side of the debate would have to eat if they were forced to admit they were wrong. Some people are above that and would genuinely welcome learning something new, but those people tend to be fairly rare birds :)

I look at it as a choice . I would imagine chemicals work but one slip ? Not good . UV works or doesn't no harm no foul. A good point made though . I am going to install a UV to be ready. Then I can go Paul's way or UV way. Myself never chemicals . As pointed out by the time the first options are exhausted it may very well be too late for chemicals anyway

 

[Freenow54]

In that case, could you point me to the evidence that, in a closed recirculating aquarium, some water never passes through the UV? I’m asking specifically about that conclusion, not the stirred tank mathematics itself.

I wonder if you could add dye to the water that could be removed by a separate filter in series with the UV . Myself I made and believe the statement that all the water cannot pas through the UV . I also believe that any organisms will happily attach themselves to the rock or substrate to Complete their cycle . Wood Ticks do it. They feed from say a moose which uses the same paths constantly the tick attaches itself feeds on the moose and then detaches itself to lay eggs on grasses ect. Then the process begins again . Maybe that's how the fish get infected (by direct contact )

 

[rtparty]

Chime in instead of criticizing seriously what you said adds nothing so add something

Add to what? This nonsense?

One side has actual evidence, the other has fairy tales not backed with any credible proof except “I don’t think X does Y” and “I’ve never needed it.” Neither point is valid or even worth wasting time on

 

[BeanAnimal]

In that case, could you point me to the evidence that, in a closed recirculating aquarium, some water never passes through the UV? I’m asking specifically about that conclusion, not the stirred tank mathematics itself.

Randy already pointed to it. It is the "Continuous Stirred Tank" problem. Defined by a decay curve: probability of never being drawn through the UV approaches zero but never hits it exactly, even assuming ideal mixing. You stated that yourself. Don't get caught up in the nuance. The untreated fraction never reaches zero at any finite time; zero is only the infinite-time limit, so the model never guarantees that 100% has passed through. That is the math, 10/3 if you will.

But let's examine what was actually said in context: Allen said 100% was guaranteed. Randy cited the CST math to show that it is not guaranteed (explained above). You are directly taking Randy’s statement out of that context and reframing it as a claim of permanent physical exclusion. Your argument is manufactured by reframed context. It should end there.

You have also made an error in your argument. It is the same asymptotic math whether you call it dilution or recirculation.

Real tanks make that worse, not better. Dead or low flow zones, mean there's no ideal mixing to begin with.

Moreover, in order to make your argument you have implied that every molecule is guaranteed to pass through. These statements set that up.

• “The question is… whether water eventually passes through the UV.”
• Low-flow areas “may take longer,” but that is “not the same as showing they never do.”

Per the model - they only work as an argument if the conclusion is that every molecule does pass through. If that's not your claim, the argument doesn't hold together. So, the answer to both questions is that in either case every water molecule is not prevented from passing through the UV, but there is no guarantee they will in finite time. Inverting the logic is not valid.

I don’t think the stirred tank analogy fits this particular discussion. The classic stirred tank model describes the replacement of water that’s continuously entering and leaving a vessel. In that scenario, the fraction of the original water approaches zero asymptotically and never reaches exactly zero in finite time.

A reef aquarium with a UV is a different system. It’s a closed, recirculating loop where the same water is continuously mixed and recirculated rather than replaced. The question isn’t whether 100% of the original water has been replaced, it’s whether water eventually passes through the UV. Those are different problems.

Addressed above, it is the same math. It is not a guarantee that it does eventually pass through, even if it may eventually pass through. Like wise when the math say n-passes for x% mixing nothing prevents faster mixing, but it is not guaranteed.

The stirred tank model doesn’t demonstrate that some water can never reach the UV. It describes replacement kinetics, not permanent exclusion from circulation. In a functioning aquarium, water is continually exchanged between high and low flow regions, so while some areas may take longer to reach the UV than others, that’s not the same as showing they never do.

Same as above. You can't make that leap from "not permanent exclusion from circulation" -- meaning nothing technically bars every molecule of water from going though the UV to the inverse that every molecule does.

 

[Randy Holmes-Farley Verified Community Expert]

I don’t think the stirred tank analogy fits this particular discussion. The classic stirred tank model describes the replacement of water that’s continuously entering and leaving a vessel. In that scenario, the fraction of the original water approaches zero asymptotically and never reaches exactly zero in finite time.

A reef aquarium with a UV is a different system. It’s a closed, recirculating loop where the same water is continuously mixed and recirculated rather than replaced. The question isn’t whether 100% of the original water has been replaced, it’s whether water eventually passes through the UV. Those are different problems.

The stirred tank model doesn’t demonstrate that some water can never reach the UV. It describes replacement kinetics, not permanent exclusion from circulation. In a functioning aquarium, water is continually exchanged between high and low flow regions, so while some areas may take longer to reach the UV than others, that’s not the same as showing they never do.

I don’t agree, and think it is the appropriate and exactly correct mathematical model if the UV kills everything. The inlet of the uv is exactly like the tank outlet and the uv
Output is exactly like the tank input with zero pathogens in it.

 

[BeanAnimal]

I don’t agree, and think it is the appropriate and exactly correct mathematical model if the UV kills everything. The inlet of the uv is exactly like the tank outlet and the uv
Output is exactly like the tank input with zero pathogens in it.

So few words, but precise.

 

[A_Blind_Reefer]

So is this why James Bond insists on his martinis being shaken, and not stirred? “Stirred martini syndrome” where not all vermouth gets mixed in? Is there a shaken tank model?

 

[BeanAnimal]

So is this why James Bond insists on his martinis being shaken, and not stirred? “Stirred martini syndrome” where not all vermouth gets mixed in? Is there a shaken tank model?

Yes:

I will explain if your screen reader does not pick it up.

 

[A_Blind_Reefer]

Yes:

I will explain if your screen reader does not pick it up.

Yeah all it says is png image

 

[Paul B]

Then I can go Paul's way or UV way. Myself never chemicals . As pointed out by the time the first options are exhausted it may very well be too late for chemicals anyway

Don't get me involved in this. This is one of the stupidest threads I have ever had the pleasure of reading.

 

[BeanAnimal]

Don't get me involved in this. This is one of the stupidest threads I have ever had the pleasure of reading.

Perhaps take your mind off it and go gift wrap my precious. It will bring you great joy.