The Bacteria Thread

Discussion in 'General Discussions and Advice' started by sihaya, 17 Nov 2007.

  1. sihaya

    sihaya

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    Ok, someone in another thread asked me a lot about bacteria which I couldn't even begin to answer in one post. But I'll give it a shot here and let people chime in (or ask further questions):

    [The role of bacteria in marine ecology could (and has) fill several large text books. The following is an uber-over-simplified overview.]


    Though bacteria play countless roles in any marine ecosystem, the role we aquarists seem to obsess about the most is that of the processing of organic waste. Since this happens the most in deep sand beds, I'll talk about them in this context...

    There are 3 basic types of benthic bacteria, aerobic (use oxygen), obligate anaerobic (can't use oxygen) and facultative anaerobic (can use oxygen if they need it). The aerobic bacteria colonize the top layer of sand (within the first few cm or so). Under this layer we get the facultative anaerobic bacteria. Then, finally, under them are the obligate anaerobic bacteria.

    Aerobic bacteria create anoxic or semi-anoxic (oxygen depleted or low-oxygen) conditions below them by rapidly consuming the oxygen in the first few inches of sand.

    Anaerobic bacteria decompose organic detritus in one of a few different ways (depending on type/functional group). For example, two such ways are via fermentation and nitrogenous oxide reduction. The facultative anaerobic bacteria that do these two things break down a lot of organic mater which can be used by other more "picky" obligate anaerobic bacteria (or other facultative anaerobic bacteria). In a way, you can think of the facultative bacteria as cutting up food, making it easier for other bacteria to use.

    Thus, facultative anaerobic bacteria (which live in low-oxygen areas) are arguably the most important to aquarists. And it gets better... these bacteria actually NEED nitrates, nitrites, and/or sulfate in order to do all this decomposing. So they're really doing two things for you at once... decomposing waste while consuming nutrients!! How wonderful! Right?

    Having these bacteria in your aquarium is almost a guarantee. HOWEVER, having enough of them (and the environments needed to maintain them) is a whole other matter. This is why I keep trying to explain that just buying a bottle of bacteria (even if it is live and even if it is the right type/species) is not going to help you (at last not significantly). You already have these bacteria. What you need to do is make sure they can LIVE in your aquarium.

    Ok, so there's a lot more I could say, but I don't want to just ramble on in one huge post... so I'll just let other people comment/ask questions and see where it goes. :)
     
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  3. Tridan

    Tridan

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    Very interesting thanks for the info.
     
  4. Mekaeel

    Mekaeel Moderator MASA Contributor

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    excellent info Sarah.thank you
     
  5. viper357

    viper357 Admin MASA Contributor

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    Great thread.

    So then is it recommended that a Deep Sand Bed (DSB) be more than 10cm deep? Would you advise maybe 15-20cm's?
     
  6. viper357

    viper357 Admin MASA Contributor

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    I would assume this is why the RDSB (Remote DSB) or more commonly knows as a "DSB in a bucket" is so efficient due to the bucket having so much more depth than 10cm's?
     
  7. sihaya

    sihaya Thread Starter

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    Sorry, I wasn't clear about the 10cm thing... this ALL happens within ~10cm. The aerobic bacteria usually stay in the top 1 to 3cm, the anaerobic in the 3 to 10cm depths. So, basically, you want a sand bed that is at least 10cm deep. However, contrary to popular belief, after 10 to 13 cm, anything deeper probably won't make any significant difference.

    Another important point is that this doesn't work so well (if at all) in coarse sand. You need FINE sand. And "silt" or "mud" is even better.

    Dean, I think remote deep sand beds are a great idea. This lets you have a 10cm fine sand bed without the headache of trying to keep all that fine sand from blowing around or getting all over everything. This is why I have my refugium for (more or less)--though I do wish I had even finer sand for it.
     
  8. sihaya

    sihaya Thread Starter

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  9. DragonReef

    DragonReef

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    Great thread and something that is so poorly understood by many aquarists.

    One of the bigger problems we face and something worth discussing is the breeding of mono cultures, of bacteria strains that are ineviatable in our closed systems.
     
  10. sihaya

    sihaya Thread Starter

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    You mean like a micro-level "old tank syndrome?"
     
  11. Reef Maniac

    Reef Maniac MASA Contributor

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    So, is Biogeek (Dr. Toonen's nickname back when he was still a student...) still active in the hobby?
     
    Last edited: 18 Nov 2007
  12. SIMS

    SIMS

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    Thanks for the info. IYO would a 25cm deep DSB be a waste of sand...
     
  13. KevinW

    KevinW

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    A question Sihaya - how much of the effectiveness of DSB's is due to water movement through (into) the sand and how much is it just diffusion along concentrations gradients of say NOx?
     
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  14. sihaya

    sihaya Thread Starter

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    That's what the research seems to suggest... that 10 - 15cm is about as much as you would ever need and any more than that wouldn't help you. If you want more filtration in the form of a sand bed, you want a bigger footprint, not a deeper bed.
     
  15. sihaya

    sihaya Thread Starter

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    Good question. From what I understand, the later is more important (the limiting factor). However, water movement is still very important. You need both.
     
  16. Mekaeel

    Mekaeel Moderator MASA Contributor

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    Sarah, i read a thread somewhere on zeovit.com.a few guys remove a cm of the DSB after a few weeks to remove detritus that settles on it,and they replace the top layer with new sand.what you think of this idea?and i must say,these are some really awsome systems
     
  17. sihaya

    sihaya Thread Starter

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    Hmmm... interesting idea. I don't know if it's necessary (or if it accomplishes anything), but I don't think it would hurt much (so long as it's just a cm). Bacteria respond/reproduce at lightening speed. They could repopulate a new 1cm layer of sand in just days (or even faster). However, I'd be somewhat concerned about the other critters this might harm (like worms and other sand turning critters).

    I do *lightly* vacuum my sand from time to time... but I try not to remove any of the sand (just any debris that might have settled on the very top).
     
  18. Mekaeel

    Mekaeel Moderator MASA Contributor

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    i do the same,just siphon off the detritus,trying my best not to disturb the the DSB.the little critters is the major concern in removing the top layer
     
  19. sihaya

    sihaya Thread Starter

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    Yeah, I agree... I don't know why it's even necessary to actually penetrate the sand bed. If the critters are pulling the debris down into the sand bed, I'd guess it's because they're doing something with it.

    Fwiw, I think the zeovit peeps are a little odd. I'd question just about anything they do. Not that they never have a good idea... I just don't think they always have much "logic" to the things they try before they try them (they're a trial and error bunch-- IMO :)).
     
  20. Mekaeel

    Mekaeel Moderator MASA Contributor

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    im actually suprised at how much of detrirus settles over the DSB although i have filter wool in my over catching out as much as possible.
    i agree with zeovit and trial and error...
     
  21. KevinW

    KevinW

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    Reason I am asking is that I have been trying to decide on a DSB design. I also thought that it is the concentrations gradients that are important. It follows then (I think) that a large surface area DSB (to cater for relatively large flow) fed directly with all the flow from the display overflow is the way to go. Flow from the DSB can then be taken through into a sump for skimming etc. Logical?
     
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