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?

If you found that hard, you'd probably have trouble tying your shoes too

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

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. 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

Exactly, so we've established that the dwell time of a skimmer is NOT related to total system volume. Just the flow through the skimmer and the skimmer volume. No that's wrong, the water won't be twice as clean, the concentration of waste will be the same in both. I'll show this later. I want to get this dwell time cleared up first. No, dwell time has nothing to do with the total system volume, you've just agreed with that with the example above. The total system volume only comes into it when you are sizing a skimmer for a particular system to get optimum dwell time. But dwell time itself is NOT a function of the total system volume. However i'm not talking about sizing skimmers for a particular system volume, we are looking at what happens when you have a system with a skimmer, then you increase the water volume of the system, WITHOUT changing the flow through the skimmer, or the skimmer itself. Right? Layton

If it helps, think of it this way Tank 1: Holds 2,000 litres with an AP902 skimmer on it with a flow of 2,000 L/hr through it, and a volume of 100 L Tank 2: Holds 1,000 litres with an AP902 skimmer on it with a flow of 2,000 L/hr through it, and a volume of 100 L Which skimmer has the longer dwell time?

You're getting off track here. We're not talking about sizing skimmers for system volume, we're talking about a skimmer which has a certain fixed flow through it, and a certain fixed volume. The dwell time of water in a skimmer is NOT determined by the total system volume. It is determined by the flow through the skimmer and the skimmer volume. Layton

How is dwell time related to total system volume? Dwell time is just a function of the volume of the skimmer, and the rate of flow through it. For example, if a skimmer has a volume of 100 Litres, and you put 1,000 litres an hour through it, you get a (very oversimplified) average measure of dwell time of 6 minutes. Again the total system volume doesn't come into it, just the flow through the skimmer and the skimmer volume. Right?

That's true, there is not such thing as 100% efficiency in practical terms. But since you mentioned it, just as an aside, lets look at the efficiency factor. It will be a function of the concentration of bubbles, bubble size, waste to bubble affinity, orientation of the waste relative to the bubble surface, bombardment rate of waste to bubbles, the surface area available for attachment etc, but it's not going to include the total system volume as a parameter or the total volume of waste in the system. So the inclusion of efficiency in the argument doesn't change the statement I make previously: All it does is unnecessarily complicate the description. Which is why I lumped it all into one thing called the "efficiency factor". Right?

Thanks for the response JDM. suphew, cracker, wasp, can I assume by your silence you agree with that post so far?

Yip. Measure at 9 am and record the level. Measure at 9 am the next day. (Without adding any additives in between measurements.) Then take the first measurement, say it was alk at 9dkH, and put it into that calculator here: http://reef.diesyst.com/ as the "Desired Alkalinity" number, then take the second measurement, say it was alk at 6dkH and put that into the calculator as the "Current Alkalinity" number, then hit "Submit Alk" Chose the supplement, most people use one of Randy's recipes for two part. That will then tell you how much you need to add every day to keep levels stable. In this example for a 1,000 litre system, it's 65 grams of baking soda a day, or 1132 mL of randy's recipe #2 per day, which you can set on a dosing pump. Same process for calcium. Layton

Or you could do it the smart way, and mix up several months worth of chemicals, and determine how much you tank uses every day, set a dosing pump to add that much. Then there's no more maintenance compared to a reactor. Plus you don't have to spend weeks tuning it. 1 day and your done. And then you don't have to worry about cleaning a reactor, making sure the outlet doesn't slowly clogg, no added phosphate, no worrying about any excess CO2, or pH. Layton

don't try and divert attention, does what I posted make sense?

If you guys are done, i'll explain step by step, why I say that adding extra water volume does nothing in terms of reducing the concentration of nurtients. I'll do this step by step, and I'll wait for agreement for you at each step before moving on, if you don't agree say why. Starting with the skimmer, we all know that skimmers work by waste dissolved in the water bumping into bubbles, and through polar interactions getting stuck to them. Lets say that the skimmer is 100% effecient, meaning that every but of waste that comes into the skimmer hits and attaches to a bubble and is removed. NOTE: this is NOT the same as running at 100% capacity. How much waste can the skimmer pull out during an hour of running? Well if we have x litres of water going through the skimmer in an hour, and each litre of that water contains y grams of waste, and because we've said the skimmer is 100% efficient it means that the waste removed in an hour is going to be x*y grams So now you can see that the skimmer output (when it's not running at 100% capcity) is independent of the volume of waste in the system. It's only related to the flow rate of water though the skimmer, and the concentration of waste in the water (and an efficiency factor defined to be 1 here). Is this correct so far?

I've always liked the look of Hamilton Island, don't know anything about the diving in that area though.

The thing is how you define overdose. With any other product, an overdose is when you actually use more than the recommended amount. However with zeovit, an overdose is when you're corals start to react badly to the dosing, even though you may be following the dosing recommendations. So with zeovit yes you can start to kill corals even when following the instructions. Granted they have tried to reduce this in recent times, by reformulating certain products, and also SIGNIFICANTLY changing the dosing scheme. They have done this for this very reason, people were having, and from what i see, still do have problems, even when following the guide. But that's just how the system works, and something to be aware of if you're going to use it. Layton

Maybe start with reading the zeoguide: This all seems very consistent with the heavy metals part of my theory. Which incidentally, wasp has not proven to be wrong. Layton

Maybe it's just me, but an additive system which recommends to cut back a tad on dosing when you notice that you're starting to kill corals with it is quite unique.

No, i'm not a scientist, i'm an engineer, (engineering = applied science) and i've studied and anyalysed these type of systems (plus a lot more advanced ones) for the last 4 years. It's not a theory at all. It's how it works. He's wrong. Look at the spreadsheet and follow it logically you'll see why. I didn't say that, all I said that it doesn't counter added waste. I'll step you through where you're going wrong tonight when I have time. Hopefully then, you'll understand it. Layton

What? You said the iron part of my theory is clearly wrong... so prove it.

prove it

nope you still don't understand.

Think about it from the point of view of the skimmer. What "knowledge" does it have about the system? All it knows is the concentration of waste in the water, and how much water is flowing through it per hour. It DOESN'T know the volume of water in the system, or the volume of waste in the system. There is no way the skimmer can change it's output based on the volume of water in the system, or the volume of waste in the system. All it has to change it's output on, is the amount of water flowing through it every hour, and the concentration of the waste in the water flowing through it. Layton

No it doesn't. Infact if the skimmer is working at 100% capacity it changes all this. Also the fact that your jumping around between increasing volume, and increasing nutrient load in your arguments in the last couple of posts isn't helping either. Wrong wrong wrong. This is what you don't understand. The output of the skimmer is directly related to the concentration of waste, it's independent of the volume of waste, so long as it's not running at 100% capacity. Look at this spread sheet. http://www.nzreefs.com/images/System%20Volume.xls And just looking at System 1 at an input of 1000 /hr, in steady state (equilibrium) you have the skimmer removing 1000 grams an hour, and the steady state concentration of waste at 2. Now increase the waste input by 5%, like you suggested a couple of posts ago, to 1050 /hr, you'll then see that the steady state skimmer output does increase 5% to 1050, and the steady state concentration of waste also rises by 5% to 2.1, which means there has been a buildup of waste in the system. Layton

Several parts to how I think zeovit does what it does. Heavy metals mainly iron in the standard base zeovit system. But also copper in other korallen zucht products. It can induce corals to bleach, from iron enrichment (reaction can be genra and species specific, and tolerances can be built in some corals). Also it appears to make them more susceptible, or promote bacterial diseases (Saharan dust). Bleached corals can be colourful. Then there are the coagulant properties of aluminium sulfate helping water clarity. A whole host of bacterial processes which come with the high nutrient environment created when running zeovit. Siderophores created from active sequestering of particular nutrients, which result in bacteria flocking.... Search for zeovit you'll find everything you want to know, plus much more.