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Thread: A Comparison Of Water Change Practices

  1. #1
    Goby

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    A Comparison Of Water Change Practices

    I've been considering for a while the question of exactly how much of the tank's nutrients am I really exporting when I do water changes. How many water changes would it take to safely export a large percentage of the tank's water over a period of a month? How does my method of changing water compare to the systems that put a little in while simultaneously removing some? I take out 17g and then replace that with 17g of mixed water that has sat over night coming up to temp being stirred and oxygenated.

    These topics may have already been covered. I wrote a paper on it for my own benefit I wanted to put some real numbers behind the routines I have with the tank. It should be noted that I don't actually do water changes every day, but what if I did? How much of the water would be changed over a period of time?

    All of these are answers I tried to answer in the following "article". That's a term I use loosely. I'm not selling anything or advocating for any particular method. I'm just trying to thoroughly understand the topic. If you see errors, feel free to let me know. I'm no scientist and this isn't official academic work. If you do disagree with the results of my "thought experiment", feel free to let me know, but please do it respectfully. We're all hobbyists with the same goal. There are no doubt issues that I have overlooked. In my paper, I did't take into account the reality that over a period of a month, nutrients are being introduced. To have a rigorous mathematical model, I would have to include "rate in" along with "rate out". That involves a level or research I don't have time or equipment to do properly.

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    Goby

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    P.S. Sorry Boomer if I should have posted this in some other forum section. I don't make it on the forum all that much and this one seemed appropriate.

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    Ez reefer
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    Very interesting.

    Auto-water-changing system sounds sweet (I bet they start at about $2000 price tag... gotta research the subject).
    Alex.

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    Wrasse
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    Very good post.
    Many people have wondered about this, but many of us lack the knowledge and math skills (as in me) to get it to the point that you have. I was lost at page 2, but understood the great graphs you drew up.
    Weather all the math is correct , or variables have not been add, you have given many of us something to think about.

    Thanks for sharing, I bet there will be a spike in salt sales soon.
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    Goby

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    Thanks for checking out the post. I was pretty surprised by what the numbers resulted in. It's like the Mythbusters episode where they find out Bigfoot really exists. What? You missed that one? It was an early episode.

    I just noticed a big typo in the article. One that could confuse someone if they're checking out how I defined the variables.

    For the variable "C" it should be defined as the original amount of "Nutrient X" that I was trying to export. I set C to 100 to represent 100% of the original amount of "X". "Y" is the percentage of the original amount of "X". It doesn't change the results listed because I calculated everything based on the correct values. Sorry about that. My biggest fault is not wanting to proof read my work.
    Last edited by halmus; 03-16-2013 at 12:22 AM.

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    Wrasse
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    Quote Originally Posted by halmus View Post
    Thanks for checking out the post. I was pretty surprised by what the numbers resulted in. It's like the Mythbusters episode where they find out Bigfoot really exists. What? You missed that one? It was an early episode.

    I just noticed a big typo in the article. One that could confuse someone if they're checking out how I defined the variables.

    For the variable "C" it should be defined as the original amount of "Nutrient X" that I was trying to export. I set C to 100 to represent 100% of the original amount of "X". "Y" is the percentage of the original amount of "X". It doesn't change the results listed because I calculated everything based on the correct values. Sorry about that. My biggest fault is not wanting to proof read my work.


    LOL,
    You lost me right after this 03-15-2013, 09:17 PM #5
    halmus
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    Thanks for checking out the post. I was pretty surprised by what the numbers resulted in. It's like the Mythbusters episode where they find out Bigfoot really exists. What? You missed that one? It was an early episode.
    You cant possibly know how you want to run your reef-system, until you have ran one.
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    RF Staff
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    No, Halmus I have no issue with your post. I have not read it all but from wha I see it looks good. This has been written about before.

    Water Changes in Reef Aquaria
    Water Changes in Reef Aquaria by Randy Holmes-Farley - Reefkeeping.com
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    Kevin
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    plagiarism? sorry! but again, its been done before and nothing beats the efficiency and efficacy of as large of a water change as one can "safely" perform. I idealistically I am with you, but practically speaking there are more relative ideals to apply.

    however the key being are you trying to export or import?
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    Goby
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    Halmus- Sorry if this is my fault!! LOL since we had just talked a little about this subject.
    Nice job and write up though, as peppie stated you lost me on some of it but the graphs
    and charts helped alot.
    Thanks
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    Hey, I was a math drop out in college and switched to the art institute but I found your "article" interesting. I've wondered the same thing and had the same original premise. I always turn my system off, syphon out the WC and then replace the newly mixed water. I've wondered if I can leave the system run which would essentially simulate your process B while I do the change, only without the benefits of a slower change. From your thought process I guess I will continue to do as I have done but know either way there is no appreciable difference.

  11. #11
    Goby

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    Thanks again to everyone that took the time to read. Thanks for the constructive criticism from those who's criticism was constructive. And then there's....

    Quote Originally Posted by kpiotrowski View Post
    plagiarism? sorry! but again, its been done before and nothing beats the efficiency and efficacy of as large of a water change as one can "safely" perform. I idealistically I am with you, but practically speaking there are more relative ideals to apply.

    however the key being are you trying to export or import?
    Please provide me with the source you're accusing me of plagiarizing. I started off the post by apologizing if this issue had already been covered. Had I known that intellectual giants like you, Kpiotrowski, had already settled the issue, I never would have brought it up. I also started off the post by saying that I'm no advocate for either method. Quite the contrary, I began studying this because I thought the "Method B" was a sham. My numbers told me differently. It's a pretty simple model, one that you learn on day two of Diff EQ. It's not like I posted up some article trying to convince anyone to buy the Santa Monica Turf Scrubber. I don't even know the name or names of the system that would change water in as it's being changed out. I just know it exists.

    On second thought, don't bother providing me the source you feel I plagiarized. I won't be following this thread anymore. I'm sorry to have wasted everyone's time here.

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    Fish Tank Freak
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    Thanks for taking the time to write this up and share it. I had forgotten the details of Randy Holmes-Farley's article and would never have taken the time to reread it.

    I was real surprised at how close the percentages are when doing water changes with method B. Having said that, I know a reefer who started doing automated 3 gallon a day WC's as described with method B and his tank took an amazing change for the better. His corals colored up more nicely and started growing faster than before. AFAIK it was the only variable that changed on his tank.

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    Kevin
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    Quote Originally Posted by kpiotrowski View Post
    plagiarism? sorry! but again, its been done before and nothing beats the efficiency and efficacy of as large of a water change as one can "safely" perform. I idealistically I am with you, but practically speaking there are more relative ideals to apply.

    however the key being are you trying to export or import?

    Maybe once, twice, a year an oppurtunity for me to drink too much arrises and the above reply was a direct result of that. Both my feet are in my mouth. I appologies for my belligerence!
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    Halmus, just in case you missed my point, I like you post and comment you on it. I was just pointing out an article done on it that you might find interesting.
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    Copepod

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    This helps me feel safe doing large water changes to get my tank back on track. As long as i get the parameters correct, so i get rid of what i want and not stress my fish. Maybe i interpreted it wrong i know my niece has better math skills than me and she's 7. Thanks for your effort in figuring this out.

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