Refugiums

[lduncan]

No, my silence indicated I have other things than this to do sometimes :lol:

I have read your posts Layton & there are a few potential holes in your argument, although that will become clearer once you move things along to wherever you want to go.

Well best to clear them up now then. It's either right of wrong. Whether it's right isn't dependant on what i'm trying to show.

However please define exactly what it is you are trying to prove? I must have lost that somewhere.

Once I know that I'll be able to detirmine the value of this discussion to me, and if I need bother with any of it.

Well someone has said that adding more water volume to an existing system reduces nutrients by diluting them. I've said that in steady state that's not true, while there is an initial dip, with it comes a drop in skimmer output which means that nutrient concentrations will end up exactly where they started.

Layton

[lduncan]

I agree with the skimmer statements Layton, but thats not what this is about.

Yes it is. We're talking about adding extra water volume to an existing system, not how to size skimmers for two independant systems.

Look at it this way:

Two tanks...

1: 1000 litres with 100kg LR, 20 corals and 20 fish, small skimmer.

2: 2000 litres with 100kg LR, 20 corals and 20 fish, larger skimmer.

Tank 1 will have the same nutrient levels as tank 2 due to the waste load produced by the inhabitants and LR, (This a set measurement), however these nutrients are spread out throughout the larger water column and are diluted. The bigger skimmer will pull these out just as fast as the smaller tank and skimmer, as it is rated for more literage.

This is where you're going wrong. I'm not talking about two different systems with two different skimmers.

This discussion started off talking about the benefit of refugiums, then someone said that the added volume the refugium provides lowers nutrients by diluting them.

So assuming people don't buy new skimmers when they add the refugium (a totally reasonable assumption given nothing was mentioned about that). When the extra volume is added, the skimmer is exactly the same, the flow through it is the same.

Layton

[suphew]

Well someone has said that adding more water volume to an existing system reduces nutrients by diluting them. I've said that in steady state that's not true, while there is an initial dip, with it comes a drop in skimmer output which means that nutrient concentrations will end up exactly where they started.

I hate to admit it, but thinking about this I might actally agree with you. What I'm not sure about is if a agree with how you came to the conculsion or maybe the way you put it was just too confusing.

How about this, a given skimmer when running as best it can is never going to be able to remove 100% of the waste so lets say when running at optimum levels the skimmer is going to still leave 5% of the waste in the water, so excluding the transient peak (i.e. when you have just fed the fish) the water in the whole system is not going to go below 5% waste because this is the best the skimmer can do. If you then increase the total volume of water, sure you will get a short term drop in % waste in each liter but this will build back up to 5% because the skimmer is not able to get it below this.

[lduncan]

I think you've got it suphew.

I'll continue though it might just make it a little clearer...

So lets look at what happens if we add more load to an existing system. What happens to the concentration of waste? Is there any increase?

First we'll define a benchmark system to compare against:

System 1

We'll define these parameters:

Skimmer Flow = 1,000 L/hr

Waste Input = 1,000 g/hr

So for the system waste concentration to be stable (at it's equilibrium point, steady state), then the skimmer output per hour has to be equal to the waste input:

1,000 g/hr = Skimmer Ouput g/hr

skimmer output = 1,000 g/hr

Remember previously we've determined that the skimmer output is equal to the flow rate through the skimmer times the concentration of waste (times an efficiency factor assumed to be 1):

1,000 g/hr = 1,000 L/hr * Concentration of waste g/L

Concentration of waste = 1000/1000 = 1 g/L

So our benchmark system has the following characteristics:

Skimmer Flow = 1,000 L/hr

Waste Input = 1,000 g/hr

Hourly Skimmer Output = 1,000 g/hr

Steady State Waste Concentration = 1 g/L

Does this make sense?

[wasp]

However please define exactly what it is you are trying to prove?

Thanks for clearing that up Layton

Now that you have explained what you are trying to prove, I see that Feelers has raised some very pertinant points that impact directly on the conclusion you are trying to draw.

I also see that thus far you have dodged trying to explain them.

Well best to clear them up now then.

Not quite that simple. Past experience will indicate I would put my viewpoint, you will counter, and this will continue ad infinitum and become circuitous. Not sure I want to commit the needed time when I already know, regardless of x*y=1, that both refugiums, and more water volume, are beneficial.

It's either right of wrong. Layton

That is the engineer talking In fact, in the real world, there are shades of grey.

Although you have not yet completed your argument, it would appear, at this stage anyway, that your whole premise is based on the export of the hypothetical skimmer with the pretend 100% efficiency, which of course does not occur in the real world. Moving away from neat hypothesis, and formulae such as x*y=1, many other factors play their part.

To show one example, there are tanks that run for years with no skimmer at all.

Also consider this. We have a hypothetical tank, running at a maxed out bioload, right on the brink of the capacity of the skimmer to export enough to keep stuff healthy. We transfer the whole thing into a tank 4 times the size. Even without any skimmer upgrade there will be an improvement in health, as there are other things than skimmer export. Now, we take the origional hypothetical maxed out tank, and transfer the whole thing into a tank 1/4 the size. It's a squeeze, but we do it. Even with the same skimmer, livestock will suffer and maybe die.

Like they say on TV Layton, Big IS Good!! :lol:

[lduncan]

Wasp i'll try and explain this

In engineering, which is REAL WORLD science, when figuring out how something works and how to control it, we use things called "models".

Depending on what you're wanting to find out, the model can be detailed and complicated or relatively simple, but you always try to use the simplest model possible which gets the job done.

What i've tried to do here is to remove the details of efficiency, and bundle it into a factor called the "efficiency factor"

Then because suphew brought it up, we looked at the efficiency factor and found that it is NOT dependant on the total system volume.

So then the efficiency doesn't change the outcome i'm trying to show here.

The final result is going to be the same, the efficiency may alter how long it takes to get there, but that's it, it doesn't change the final result.

That's the reason why I haven't complicated things by including efficiency, and made the assumption, for the sake of simplicity, that it is 100%.

Wasp you are dragging in other factors which don't have anything to do with adding water volume.

What I'm talking about, is the claim that adding water volume can lower nutrient concentrations in the system on a sustained basis by dilution. It doesn't. In terms of waste concentrations, doubling the volume of water in the system will have no steady state effect on them.

Layton

[lduncan]

Also consider this. We have a hypothetical tank, running at a maxed out bioload, right on the brink of the capacity of the skimmer to export enough to keep stuff healthy. We transfer the whole thing into a tank 4 times the size. Even without any skimmer upgrade there will be an improvement in health, as there are other things than skimmer export.

But that doesn't mean waste concentrations have changed. The one think which added volume is good for is there is a larger pool of resources for animals, (think alk, mag, calcium etc), the large pool means that the relative levels change more slowly, and if resource limitation was an issue in the smaller tank, sure, going to a large tank is going to make a difference.

BUT what going to a larger system volume does NOT change is the concentration of waste in the water.

Now, we take the origional hypothetical maxed out tank, and transfer the whole thing into a tank 1/4 the size. It's a squeeze, but we do it. Even with the same skimmer, livestock will suffer and maybe die.

Like they say on TV Layton, Big IS Good!! :lol:

Sure but it still won't change the concentration of waste in the water. The animals may suffer and die from resource limitation. As parameters like calcium, magnesium, dissolved oxygen etc may drop rapidly, if the aquarist doesn't make sure they are as stable as they were in the larger volume tank.

So, again, the concentration of waste in a system is NOT dependant on the volume of water it holds, just the flow through the skimmer, the efficiency, and the input of waste

Where is all this going? Well if you understand this, you understand from a skimmer point of view, how to lower the concentration of nutrients in your tank and sustain it. (And just to recap, it can't be done by simply adding water volume)

Layton

[JDM]

i agree layton, it makes sense to me.

[wasp]

Wasp i'll try and explain this

In engineering, which is REAL WORLD science, when figuring out how something works and how to control it, we use things called "models".

Depending on what you're wanting to find out, the model can be detailed and complicated or relatively simple, but you always try to use the simplest model possible which gets the job done.

What i've tried to do here is to remove the details of efficiency, and bundle it into a factor called the "efficiency factor"

Then because suphew brought it up, we looked at the efficiency factor and found that it is NOT dependant on the total system volume.

So then the efficiency doesn't change the outcome i'm trying to show here.

The final result is going to be the same, the efficiency may alter how long it takes to get there, but that's it, it doesn't change the final result.

That's the reason why I haven't complicated things by including efficiency, and made the assumption, for the sake of simplicity, that it is 100%.

Layton

I know all that, and I concur. I do not even automatically dissagree with everything you say :lol:. I do not have a problem with your use of hypothetical models, provided they are based on reality.

Wasp you are dragging in other factors which don't have anything to do with adding water volume.

Layton

Such as?

What I'm talking about, is the claim that adding water volume can lower nutrient concentrations in the system on a sustained basis by dilution.

Layton

That is very narrow Layton. Should be easy to prove.

Does it reflect all the processes happening in a real tank? No.

What I'm talking about, is the claim that adding water volume can lower nutrient concentrations in the system on a sustained basis by dilution. It doesn't. In terms of waste concentrations, doubling the volume of water in the system will have no steady state effect on them.

Layton

What in fact you are trying to do is eliminate a lot of real world variables that play their part, and just introduce a bunch of variables that you define as x, y, abc, or whatever. Then having narrowed & defined these variables, use logic to arrive at a mathematically precise conclusion.

In the past I have been sometimes exasperated at your use of flawed logic. However in this instance, your logic is perfect, simple even. The problem is in the variables it is based on, they are not all there.

For the discussion to be of any use to me anyway, it must relate to a real world tank, rather than a simple x amount of dirt, x amount of skimming type thing that fails to consider the hundreds of other processes that happen in a tank, and are affected by water volume.

So, some of these other variables that I do not see in your formulae, have been raised by Feelers. Have you considered any of these yet?

[suphew]

Then because suphew brought it up, we looked at the efficiency factor and found that it is NOT dependant on the total system volume.

I still disagree with you here, and we didn't find that it wasn't dependant at all. They aren't directly related, but they are related indirectly because of the required dwell time. for example if you have a huge tank and a tiny skimmer your turn over in the skimmer needs to be so high to process all the water that dwell time will end so low the efficiency will go out the window, (or you could run the correct dwell time, but then a large amount of the water would never see the skimmer). The same is less likely but could happen in the reverse, a huge skimmer on tiny tank, at some point there would be a limit to how fast you can get the water out of the tank into the skimmer so the dwell time becomes too long, wasting efficiency.

If memory serves my correctly this whole thing didn't start because you stated the nutirant levels would stay the same. It started because you stated that adding a refuge would increase bioload and that this was a negative because of extra nutirants. I think you have managed to pretty soundly prove yourself wrong, because as you have proven (to me anyway) unless the skimmer hits full capicity it doesn't matter too much if you increase or decrease, volume, bioload, etc, the skimmer will continue to lower the water to the same nutirant level as dictated by how efficient it is.

[lduncan]

I know all that, and I concur. I do not even automatically dissagree with everything you say :lol:. I do not have a problem with your use of hypothetical models, provided they are based on reality.

The reasons they are called models is because they ARE based on reality. They model reality. Models can never be hypothetical.

That is very narrow Layton. Should be easy to prove.

Does it reflect all the processes happening in a real tank? No.

Not narrow at all. And yes you will find that this happens in a real tank.

What in fact you are trying to do is eliminate a lot of real world variables that play their part, and just introduce a bunch of variables that you define as x, y, abc, or whatever. Then having narrowed & defined these variables, use logic to arrive at a mathematically precise conclusion.

So I giving you a chance to say what those variables are. All i'm talking about is adding extra volume to the tank.

However in this instance, your logic is perfect, simple even. The problem is in the variables it is based on, they are not all there.

So what other variables are there?

For the discussion to be of any use to me anyway, it must relate to a real world tank, rather than a simple x amount of dirt, x amount of skimming type thing that fails to consider the hundreds of other processes that happen in a tank, and are affected by water volume.

I think you are getting so bogged down with unnecessary detail, that you can't see the forest from the trees. At it's simplest, a tank has a certain input of waste, and a certain output of waste. You don't need to get into the details of how the waste is created etc.

Layton

[puttputt]

Whats the point of this Layton??

At the beginning of this thread, it was generally agreed that refugiums (thats right, look at the subject) were not good for nutrient export. Everyone agreed.

They have a number of other points that are positive, including adding system volume, which does provide stability, I don't think there is any argument in that, and is also good for dilution of nutrients in a one off problem or mistake albeit short term, i.e. if I accidently tip a whole cannister of food into my tank, or a large anenome dies. I'd much rather have either of these happen in a 1000l thank than a 250l tank.

Don't you think you are spending alot of unnecessary time explaining a theory that no one is really going to ever use.

I think we all understand that if a skimmer can only remove 80% of the waste products, you can dilute all you want, but eventually all water will end up with the same % of nutrient as the smaller volume started with, skimmer etc being equal.

What if you ref contained live rock, live sand, macro algae etc. They all remove nutrients as well as the skimmer. Can't see the point in this.

[lduncan]

Well it comes back to this post:

Something else to think about....

If you have a fuge, then you need a tank, (unless you have a sump and then you use that), But if you add afuge and place sand etc, you are also adding extra water to the system which will counter the bioload in the first place.

i.e: add fuge, add 200 litres, add bioload.

It cancels each other, so the answer...BENEFIT!!

Which I said was wrong and not a valid point. Then it went from there people saying I was wrong, that water volume diluted nutrients so your tank would be cleaner.

Which is all clearly wrong. And a point which some people still can't see. Hence the continuing debate.

Simply adding water volume does nothing for lowering nutrients in the steady state.

If you can follow what i've been saying, then you'll have a good idea on how to, and how not to, lower nutrient concentrations permanently.

Layton

[puttputt]

from what I read in Crackers statement, he's simply saying more water can support a higher bioload. Surely you dont disaggree with that. I can't see where he claimed that your nutrients will be lower?

Alot of us run with almost 0 Nitrate and 0 Phospahate so nutrient dilution isn't an issue.

[wasp]

The reasons they are called models is because they ARE based on reality. They model reality. Models can never be hypothetical.

Layton

Sorry dude I can't buy that. A person can build a model on anything he chooses. Might be real, might not be real.

Not narrow at all. And yes you will find that this happens in a real tank.

Layton

Yes it is narrow. While it happens in a real tank, it narrows out other factors that come into play.

I think you are getting so bogged down with unnecessary detail, that you can't see the forest from the trees. Layton

Again, such as?

[jetskisteve]

I think we should consider Chims point *Yawn*

[puttputt]

[wasp]

Yes. Amazing the length and complexity someone will go to, to split hairs with Craig.

Who by the way, isn't playing :lol: .

And the best model is a real tank. I have seen Craigs one, he has nothing to prove.

[KP]

Sorry dude I can't buy that. A person can build a model on anything he chooses. Might be real, might not be real.

Yes it is narrow. While it happens in a real tank, it narrows out other factors that come into play.

Again, such as?

Had to do it, soo many quotes

[puttputt]

And the best model is a real tank. I have seen Craigs one, he has nothing to prove.

now, ain't that the truth.

[Pies]

So we agree then: more water = good.

[puttputt]

There was only one who did not agree.

[Pies]

OK. We = Everyone - Layton.

[wasp]

OK. We = Everyone - Layton.

No wrong.

We = x

Everyone = y

Layton = z

concurrence is x - z = y

[Pies]

I don't understand, can you plot that on a graph for me?