Deep sand bed parameters

Discussion in 'Biological/Natural Filtration and Deep Sand Beds' started by Franske, 19 May 2009.

  1. Franske

    Franske

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    Im wondering,when you set up a dsb for the first time and there is phosphates or other stuff like amonia or so in the water that you start the tank with,aswell as water with a wrong ph,and water thats salinity isnt perfect(example:if you fill your tank with fw and then add the dsb and then the salt meaning there is fw at the bottom of your dsb),what happens with this water that sits at the bottom of your dsb and does its parameters ever become the same as your tanks?
     
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  3. zee

    zee

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    Good question, I`m tagging along on this one!
     
  4. RiaanP

    RiaanP Moderator

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    I found that air bubbles trapped in the sand, stays there.
    So I believe that the bottom 5cm sand do not change water as quickly as you think, else it will not be an oxygen depleted zone. So from that I can just say the bottom part will stay whatever it was.

    Question was it freshwater, like in tap water or RO water?

    I will give the DSB a good turnover. Depending on how old it is. "New", I will take all the sand out, fill the sump with water and drop the sand back, cup by cup, so that air bubbles can not be captured. Problem solved.

    Old? hmmm.
     
  5. Reef Maniac

    Reef Maniac MASA Contributor

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    Interesting question...

    If there was a difference in salinity between the "bottom" water and the rest of the tank, osmotic preasure will cause the salinities in both layers to eventually become the same, although if there is absolutely no water movement in the tank then it could take a while...

    Hennie
     
  6. Franske

    Franske Thread Starter

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    Thanks alot that makes sense,wil osmotic presure do the same with other parameters like ph nitrates etc
     
  7. jacquesb

    jacquesb Retired Moderator

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    Yes Frans - osmotic pressure -> meaning: EVERYTING ENDS UP IN EQUILIBRIUM, over a period of time....... It HAS to.... law of nature....
     
  8. riyadhessa

    riyadhessa

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    Brilliant question and answered
     
  9. RiaanP

    RiaanP Moderator

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    Question is just, how long will it take?

    My conclusion is that if bottom part of a DSB is an oxygen depleted zone, then this natural balancing act is not as quick as we think. Also thinking about Pleniums, and the way they work, I doubt seriously if this balancing act is anything fast. The bacteria at the bottom are capable to reduce oxygen levels totally so that they use the NO3 Nitrite to survive in that space. So either there is a small little house full of bacteria, or the process is extreeeeemlllyyyy sloooowwww.

    And the water in there is pretty much trapped. No movement at all.
    So it should be like a shooter, B52, Springbokkie or Black Russian. The liquid do not mix, only in your stomach and ... well that is another story.
     
  10. Franske

    Franske Thread Starter

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    I was told on another forum that the other lifefroms deplete the oxygen before it reaches the bottom of the dsb,and talked to some other ingeneers along with me in the res and they also said that it will eventually spread evenly,but yes i would also like to know how long and what happens with parameters like ph etc,coz ive read that aragonite only disolves at low ph at the bottom of a dsb and how does that happen if the ph of the sump and dsb eventually become the same,or am I mistaken
     
  11. Reef Maniac

    Reef Maniac MASA Contributor

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    OK, I think we are talking about two processes here:

    1. Nothing "eats" the salinity, so this should reach equilibrium at some point in time due to osmosis (although I don't have any idea of how long it will take...)

    2. The oxygen content, nitrate level, etc. is continuously modified by external processes, such as the depletion of the O2 by bacteria and small critters living in the sand bed. Even though osmotic pressure would try to even this out, the bacterial "engine" will win, and maintain the level difference. The same goes for the higher nitrate level originating in the top of the DLSB, this moving down through osmosis, but continuously being converted to nitrogen in the bottom region of the DLSB.

    Hennie
     
  12. jacquesb

    jacquesb Retired Moderator

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    Riaan / Frans - it's the same as the proverbial question: "How long is a piece of string"...

    The best (and unfortunately, the most vague) answer I can give you both: "it takes as long as it takes"....

    Remember: The seas and oceans are millions of years old...... The "sand beds" all over the sea, took their own sweet time in developing/perfecting this process....

    We cannot haste nature..... even if we want to....

    That's part of the answer to the question: when is a marine tank "mature".....
     
  13. RiaanP

    RiaanP Moderator

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    so, if DSB is "new" / "young" / inmature / teenager. :)
    Then just go and stir the sand to speed up this process and get it over with. Then we do not need to worry how long is the string. :)

    If it is old, then we have to find out how long is the string.
     
  14. jacquesb

    jacquesb Retired Moderator

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