Refugiums

[wasp]

[puttputt]

[JDM]

:lol:

[lduncan]

A bumper sticker comes to mind here:

Never argue with idiots. They will bring you down to their level and beat you with experience.

[wasp]

.

[cracker]

:lol:

Good thread.

Welcome back Pie man.

[Feelers]

Still waiting for an answer Layton,

What will happen to the nitrate levels/phospherous levels in your tank if you doubled the system volume?

Would there be a measurable increase/change? I'm aware that there probably isnt enough info to work it out but I've never seen anyone mention an increase after addition of a sump etc.

[lduncan]

Ok,

So now we take the same system as before, but increase the waste input 5% to 1,050 g/hr

System 2

Skimmer Flow: 1,000 L/hr

Waste Input: 1,050 g/hr

So doing the same as before, for the concentration of waste to be stable (at equilibrium point, steady state), then the skimmer outpur per hour has to be equal to the waste input per hour:

skimmer output = 1,050 g/hr

As you can see, the skimmer ouput has increased by 5% in response the the increase in waste input. Now what about the concentration of waste? Has it increase?

Well as before, the skimmer output is equal to the flow rate through the skimmer times the concentration of waste in the water:

1,050 g/hr = 1,000 L/hr * Concentration of waste g/L

Concentration of waste = 1050/1000 = 1.05 g/L

So not only does the skimmer output increase in response to increase in waste input, the concentration of waste in the water also increases proportionally.

So now what happens to waste concentrations when you add more water volume to a system?

Well, in the stready state, absolutely nothing. Athough intitally there will be a drop in waste concentrations, there is also a corresponding drop in skimmer output, but eventually the concentrations come back to what they were at the beginning, before the extra water was added.

The skimmer output and concentration of waste is independant from the total system volume.

[skippy]

Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaahhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh

I thought it had died, but no - like a phoenix from the ashes - it rises again

I'm happy to say that I got confused on page 1 and have nothing to add Will leave it to the boffins and the stirrers.

Funny read though

[chimera]

:lol:

[wasp]

The question was :-

Still waiting for an answer Layton,

What will happen to the nitrate levels/phospherous levels in your tank if you doubled the system volume?

I'm keen to see you explain this also Layton, but I did not see nitrate mentioned in your "answer" at all.

But hey, I do sympathise.

Being forced to hang out with idiots must be rough on a mis-understood genius .

[lduncan]

What's the response of to nitrate / phosphate levels increase system water volume? In the steady state, nothing, they stay at the same level.

And trust me, i'm no genius, misunderstood or otherwise. Some people I know, know more about a lot wider variety of things than I do.

[wasp]

Dude I can't even understand your answer. "In the steady state"? Without any context / explanation I have no idea what you might mean by that.

And, "nothing, they stay at the same level". Kinda leaves me unsatisfied. Some kind of explanation is needed.

[wasp]

Some people I know, know more about a lot wider variety of things than I do.

Really!! I think I have yet to meet one of them! :lol:

[lduncan]

Dude I can't even understand your answer. "In the steady state"? Without any context / explanation I have no idea what you might mean by that.

Well when you look at these types of systems there are two analysis you can look at, depending on what's important to you.

Either transients, or steady state.

Think of it like this, you have a spring with one end fixed to a table, then you give the top of it a flick (this is called an "impulse"), it starts to vibrate. The transient response is what happens throughout the whole time after it has been flicked ie: the motion of the vibration. The steady state, is the state the system tends to after the transients have been and done (the long term effects resulting from the "impulse"). In the example of the spring, the steady state response is that the spring stays in the same position as it was before the impulse ( the flick ).

For example in my specific field, transient analysis is important so that components don't overheat and explode, or control systems don't become unstable. But for this discussion here, we're only really interested in the permanent effects of changes, hence the term "steady state".

And, "nothing, they stay at the same level". Kinda leaves me unsatisfied. Some kind of explanation is needed.

What more do you want? It's kind of self explanatory, isn't it? Adding water doesn't change the levels of these parameters in the steady state.

Layton

[wasp]

Thanks for explaining what you mean by steady state.

What more do you want? It's kind of self explanatory, isn't it? Layton

For openers, you don't address what you mean by "levels". Do you mean measureable levels in the water, or total level in the system, before, and after, volume is added? That is the whole crux of the question isn't it?

[lduncan]

concentrations stay the same

pool totals increase proportionally to the volume of water added

[wasp]

For nitrate and phosphate?

You sure about that?

How do you know?

[Pies]

And trust me, i'm no genius, misunderstood or otherwise. Some people I know, know more about a lot wider variety of things than I do.

lol

[wasp]

In the case of nitrate, check this, I’ve done it special in clever engineer language! :lol: :-

We are of course considering the result, in “steady state†:lol:

System size (volume) = x

Amount of rock = y

Amount of nitrate rock processes each day = q

Amount of food going into the system = t

Total nitrate in system = b

Nitrate concentration in water = a

If x=1, y=1, t=1, then q=z

If x=1, y=1, q=1, t=1, b=1, a=1

If x=2, y=1, q=1, t=1, b=1, a= ½

If x= ½, y=1, q=1, t=1, b=1, a=2 :D

[Jeroen]

Amazing discussion ! Wonder if everybody talks about the same subject.

So why not join in 8) and before people ask... I am an engineer too Even worse I am an engineer in applied physics. Although said that I always like the applied bit. There is nothing more valuable then field data.

Back to the story. As I see it we have here several subjects. 1) The influence of a skimmer on dissolved organic compounds (DOC) in the system, 2) The production of DOC in the aquarium and how much a refugium contributes to this, 3) The effect of the system volume on DOC (longterm).

It sounds like Layton is only talking about how a skimmer affects the DOC. On this I slightly disagree with him. The output of a skimmer depends on a lot of variables of which the particle size of the DOC is very important and this will vary over a very wide range in the aquarium. You will find that with equipment like skimmers that as long as you stay within the operating range of the skimmer the output hardly change when changing the concentration on the inlet (I have never seen a linear relation here in the field).

To gain understanding of system models are very useful but only if you also understand the shortcomings of the model used. I have often discussion with process engineers about what the model predicts and what we find in the field. I have noticed that there are a lot of people that prefer to belief the models instead of the data from the field (To me these are the engineers that don't use the word applied). I found a very interesting model for skimming on the web (http://www.reefs.org/library/talklog/d_ ... 12499.html). It is does not state that this is the absolute model but looks at the influence of certain parameters on the system and states several of its limitations. I think it will entertain some us.

The second point is more interesting and important to the subject. Unfortunately this is not an engineers subject and we have to rely on Feelers here . I really enjoy his input. It helps me to understand the system much better. I am still very new to the aquarium hobby and this part is not my strongest point. If I understand it well we like the refugium to be a good filter to remove ammonia /nitrite / nitrate but are worried about the extra bio-load it might give (organics). To me this sound like that there is an optimal filter size and if you have too much filter area (rock / sand) you start to pollute your system. Is this true Feelers?

The last point is the influence of water volume on longterm DOC levels keeping everything else the same. There is no change in production of DOC or removal of DOC therefore the water volume will not influence the DOC level in the system. If the skimmer is the only part that removes DOC then whatever the tank volume the DOC will settle at the skimmers output of DOC.

I just wish understanding all in the aquarium was as simple as engineering.

Jeroen

[wasp]

Good post.

Engineers CAN make sense! :lol:

You have raised a number of other points Jeroen, and as you have realised correctly, Laytons argument is based on the idea that skimmer export is the whole story.

To me this is where the argument falls over, as nitrate for example, is processed by liverock, and export can be entirely independant of skimming. A lot of other pitfalls in the argument also the whole thing is very logical, but too narrowly defined. Real world anecdotal evidence would also be that more volume is better for water quality.

The end result of this argument will be that Layton will prove the point he is trying to make, within the narrow confines he has set, but will be unable to prove that more volume in a tank is not good for water quality because that is not the case, plus he is the only one who believes it.

Anyway, good to see you come in as a neutral commentator, I'll let Feelers answer the questions you have posed to him.

[lduncan]

Hmm, I should have checked out the web, it would have saved me a lot of typing. The link that Jeroen found pretty much covers what i've been saying:

http://www.reefs.org/library/talklog/d_ ... 12499.html

Namely, that increasing water volume doesn't change nutrient concentrations.

Layton

[lduncan]

To me this is where the argument falls over, as nitrate for example, is processed by liverock, and export can be entirely independant of skimming. A lot of other pitfalls in the argument also the whole thing is very logical, but too narrowly defined.

So, how does adding water volume, make the amount of rock in a system increase?

Real world anecdotal evidence would also be that more volume is better for water quality.

Better for water quality, or better for livestock health? There is a difference.

The end result of this argument will be that Layton will prove the point he is trying to make, within the narrow confines he has set, but will be unable to prove that more volume in a tank is not good for water quality because that is not the case, plus he is the only one who believes it.

The confines aren't narrow at all, and it seems I'm not the only one with this opinion. The guy in that link obviously thinks so too.

Anyway, good to see you come in as a neutral commentator, I'll let Feelers answer the questions you have posed to him.

Of course I'm biased because... well by the looks of it, because I don't agree with wasp :-?

[wasp]

Read the article again Layton :lol: .

You will see it is about skimmer efficiency at removing DOC's at various tank volumes.

Does it discuss nitrate export by liverock? No.

Does it discuss a whole host of other factors that come into play? No.

Is it a real tank? No. It is a simulator, related to skimmer export only.

This confirms exactly what i have been saying, your modeling is based on skimmer export only and is too narrow.

As I said, the end result of this argument will be that you will prove your point within the narrow confines you have set. Your linked article would tend to confirm that. But you will not prove that more volume in a real tank is not good for water quality, because in a real tank, rather than a narrowly defined model, Big IS Good! :lol: