Depth of deep sand beds?

Discussion in 'Biological/Natural Filtration and Deep Sand Beds' started by Rod, 15 Feb 2009.

  1. Rod

    Rod

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    There are many threads suggesting a depth of 300 mm (12 inches, for those who still use gallons) for a deep sand bed.
    Is there any gain in increasing the depth?
    We could go as deep as 2 meters in a system being planned by Peterb.
    This would be in a 10000 liter drum as an add on to his existing filtration.
    Any one?
     
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  3. Peter Bee

    Peter Bee

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    thanks for the help
    peter
     
  4. Peter Bee

    Peter Bee

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    hey
    just another question, i would like to fill the rest of the drum
    with rock. any problems with that besides the sediment build up around the bottom of the rocks,
    peter
     
  5. Tobes

    Tobes Retired Moderator

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    It depends on the grain size of the sand. Sugarfine sand will be adequate at a depth of 15cm to ensure natural nitrate reduction. The coarser the sand, the deeper the bed needs to be. If you're using aragonite, take into account it has a "half life" of about 2 years. Meaning if you have a substrate of 3cm it will be reduced to 1.5cm in 2 years time - the same for DSB's. Just make sure that if your DSB looses depth over a 2 or so years time, you need to add more aragonite to prevent it from failing in natural nitrate reduction (NNR). Anything deeper than 15 - 20cm with sugerfine sand is a waste. You don't need deeper than 15cm, what will help is a bigger surface area.

    If you wanna add rock on top of your DSB, use egg crate suspended about 50 - 100mm on pieces of PVC pipes and put the live rock on top of that. This will ensure adequate flow under the live rock and won't restict gas exchange or releasing of nitrogen bubbles.
     
  6. ziyaadb

    ziyaadb

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    Hi Gents from what i have read over time if a DSB is too deep you have a possibility of the gas at the bottom getting toxic and releasing sulphides/phates into the water column. But lets wait for the experts
     
  7. Bob the (reef)builder

    Bob the (reef)builder

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    You will anoxic areas with very deap beds but that is inlikely to be a big problem unless the bed is disturbed.

    Being deaper than required though for the partical size is unproductive.
     
  8. Peter Bee

    Peter Bee

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    hi tobes
    thanks for the info, i thought about the egg crate thing but the top of the drum has a small hole on top, i will try make a plan to do something like you say. there are two drums one 5000l and a 10000l. the 5000l is just for extra water volume and the 10000l is a extra filter. these are being added to my pond in my shop so i can run my new tanks through the system as well. so when it is all done i should end up with about 45000 to 50000l in total. i just hope it all works out like planned, thats why i am looking for advice.if it works it should be a fantastic if not well i will just blame rod he had a lot to do with me building all this.



    thanks
    peter
     
  9. Tobes

    Tobes Retired Moderator

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    That sounds great, you should start a thread on this setup and post some pictures for us. Good luck with it :)
     
  10. sihaya

    sihaya

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    No... there's no advantage known over 150mm even... probably not much advantage even past 100mm.

    Not worth it... likely won't help.


    Cheers
     
  11. kalkwasser

    kalkwasser

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    I agree with Sihaya.
     
  12. sihaya

    sihaya

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    Thanks Kalk. I'm not just pulling this out my skimmer... I'm repeating what Toonen (and many other benthic marine biologists) report (as far as I understand). The processing of nutrients such as Nitrates, Nitrites, etc. pretty much stops (or becomes negligible) past the 150mm mark...
     
  13. viper357

    viper357 Admin MASA Contributor

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    So in that case would surface area be a lot more important as opposed to depth? It's a given that a DSB should be between 100mm and 150mm, should we be aiming for as big a surface area as possible?
     
  14. sihaya

    sihaya

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    Yes... definitely! If you want to go sand bed crazy... get a bunch of "tray shaped" rubber containers (like the kind designed to slide under a bed)... the ones that are shallow, but wide and long. These would likely make for great "trays" of sand beds. Come to think of it... I don't know why I've never seen this done before. I suppose most people are too hung up and depth to realize that what they really want is area.
     
  15. scubaninja

    scubaninja

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    sorry to butt in, but this is what i've always thought, from when i was first told it must 150mm deep i reasoned it should have as large a surface area as possible. Stands to reason that if your depth is not your greatest factor on efficiency your volume would be, and if you cant increase depth you can only increase surface area:p
     
  16. viper357

    viper357 Admin MASA Contributor

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    Cool, so we need to concentrate on as big a surface area as possible.

    Now what about lighting? If you have a tank separate from your sump that is a dedicated DSB, is there any need or benefit to lighting the DSB? Could we keep the DSB in complete darkness to try and also promote the growth of sponges?
     
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