1. Neil H

    Neil H Moderator MASA Contributor

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    I have been toying with an idea for some time with all the discussion on DSB's on the forum lately!

    Here goes ......

    I am not concerned about substrate depth or type as this has been covered in many articles, what i am concerned about is the flow, and more specifically the correct type of flow ..... we are trying to create very specific environments for certain types of bacteria....

    99.9% of sumps that i have seen, including my own are built with glass dividers on either side of the DSB which rise up in the order of say 10cm (some much more) ABOVE the level of the DSB, i.e. each glass panel is 10cm plus the depth of the DSB. the water level is then traditionally some 3 cm above this glass height....

    what if this is wrong?

    why i say this is....flow........ how is that water travelling over the DSB? i would argue that most of the water is moving over the DSB in the top 3 cm, and is not getting into contact with the DSB itself..... Many of us have cheato on top of the BSD..... this is not pushed to the one side of the dsb, in most cases it is stagnant, slowly tumbling if you are very lucky .....

    The way I understand a DSB is that it needs two distinct area's one oxygen rich and one oxygen poor..... both are equally important and the bacteria from the oxygen rich are provide "food" for the oxygen poor area, there is a reaction or process that must occur.....

    Are we providing the correct interface in traditional sumps? the old water flows over the top and i think the top of the DSB is oxygen poor in comparison to the rest of the tank as a result of stagnant area's ...... Are we confusing a fuge with a sand bed with a DSB?

    What about this as an alternative ....... ?? chop the extra 10cm off the dividers, have a seperate chamber for the chaeto etc and let a DSB be a DSB


    [​IMG]

    you now bring tank water into contact with the DSB, you have the oxygen rich area and oxygen poor area ......

    Thought on this please
     
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  3. SchyffS

    SchyffS Reef Aquarist

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    Anaerobic zone in dsb

    Hi Neil, i have also done lots of reading on the subject of flow.
    Perhaps we must isolate the two areas so that each can be analysed seperately to understand how exactly it works and what conditions would be ideal for each, namely aerobic and non aerobic areas.

    Im gonna concentrate on the anaerobic portion of the dsb for now:
    I would rather say that the anaerobic portion requires NO3 rich water instead of oxygen deprived water, its not possible to provide O2 deprived water....the logic is that the bacteria breaks down NO3 by using up the 1 oxygen molecule and then releases NO2 into the substrate in the form of a gas, better known as nitrogen gas(denitrification)...and so its termed oxygen poor.
    So, the water flow needs to be fairly slow to ensure there is enough settlement of such water....not stagnant though.
    A simple test is to take tea and sprinkle at the start of the dsb and see if the tea settles. According to the research ive done this is the way to test the flow rate. I cant convert this to litres/hour.
    The proof of this is my own sump see thread
    Reef octopus dnw-110-6520 setup - Marine Aquariums of South Africa
    After starting the sump up the wrong way i ended up with a very different sump design catering for a slower flow over the dsb.
    The only problem with my sump was that it was too small.
    However see
    DIY 4
    Therefore my conclusion is that the flow rate should be slow.

    :whistling:
     
    Last edited: 10 Jan 2011
  4. Neil H

    Neil H Thread Starter Moderator MASA Contributor

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    Last edited by a moderator: 26 Nov 2015
  5. SchyffS

    SchyffS Reef Aquarist

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    @ NeilH, can you redraw your proposed sump so that it can be better understood
    emm, i cant follow what the flow does in the pic of post 1
     
  6. RiaanP

    RiaanP Moderator

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    Yip, I moved my cheato to its own 90L tank. A lot better.
    Now i can see what is going on on my DSB. But i found that worms and pods are now without a home. So i added some empty shells, just lying around. And the bristle worms prefer that. And i got one 10cm dead coral base and 4 or 5 really small LR pieces. And the worms like to crawl in under that. So yes, I believe some stuff must still be around to provide at least some shelter.

    another point I tried to highlight before, it is not the old rule of 3 to 5 times the display volume that must run over the DSB per hour. But rether the strength of the flow. Meaning that a DSB of 300mm and another of 600mm wide and both the same lenght, on same size display, will not be the same. So to have the same flow rate, the 600mm wide must have a return pump double that of the 300mm. So that results in a new rule (for that setup) of between 6 and 10 times the tank turnover. Basicaly confirming what Schyffs said.
     
  7. Neil H

    Neil H Thread Starter Moderator MASA Contributor

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    its very schematic, simply showing x chamber before the dsb which may have a skimmer in in and Y chamber after the dsb which may have reactors and pumps in in, the idea is really the geometry of the DSb chamber and the flow over it, not what happens before or after
     
  8. RiaanP

    RiaanP Moderator

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    I'm also going to build a new sump soon. And there is still another thing that bothered me, and I think I got it eventually. It is as you mention, the flow that just happens to be over the top, and not really mixing or entering into the DSB.

    So here, I'm leaning towards "baffles" at the entrance side. Skimmer compartment. Then glass panel that is open 2 to 3cm at the bottom, leading into first baffle. Baffle is 2 to 3cm wide. Now the trick. Instead of running the water over the next glass pane, that pane should consist of two pieces of glass, Bottom one, max 20cm high, then a gap of 2 or 3cm, (same as the under space under first glass pane) then another glass pane that will be high enough to me at least 1cm above total water volume. So first pane and second pane at same height, and both 1 cm higher than the pane before the return pump.

    then I will go for at least 150mm or more water depth above the DSB sand.

    Positives,
    Less detritus around skimmer, as flow is out the bottom of that chamber.
    Max water volume for DSB. As high as can be without drowning the skimmer, or else lift the skimmer.
    No water running over the top part of DSB. Water enters in the middle of the water column above the DSB.

    Note, no baffles at the exit side of the DSB. And do not repeat the slot idea at exit side. Because then you could end up with gunk collecting on the water surface in the DSB chamber.
     
  9. Neil H

    Neil H Thread Starter Moderator MASA Contributor

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    i dont think we are talking about the same thing here guys, i am not talking about the rate of flow, i am talking about the type of flow, my argument is that good shallow laminar flow over the DSB will induce propper exchange of NO3 rich water to bacteria which convert it to NO2, my understanding is that this area has to be Oxygen poor for the survival of this bacteria

    what i am saying is that laminar flow over the surface of the DSB is better than flow that happens 10 or 15cm above the DSB and the DSb surface itself is stagnant.

    I was watching TV last night where they documented a 5% increase in Oxygen content in "shark holes" off the coast of mauritius, i would argue thus that it is possible to create area's of low oxygen content in our tanks and such area's would be in stagnant parts of our tanks.......
     
  10. Neil H

    Neil H Thread Starter Moderator MASA Contributor

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    can you put a sketch of this idea up for us pleas Riaan, battling to follow your logic
     
  11. dallasg

    dallasg Moderator MASA Contributor

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    yes this is how the RDSB's work that are made in a bucket, all the RC guys use this method as it provides only an inch of laminar water flow over the sand.

    so we tank a 75L dustbin, fill it with sand 7cm from the top, flow water 2cm above and drain, bam a very deep dsb
     
  12. Neil H

    Neil H Thread Starter Moderator MASA Contributor

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    As far as i am concerned, a DSB and a RDSB are the same thing, just that a RDSB is remote to the tank (usually as a result of space issues) and hence the name.

    IF so many international people are saying a RDSB is good (and RDSB's are as Dallas has described with one inch of laminar flow) then i argue that what we call DSB's are simply glorified fuges which only serve a token DSB function and are not effective at all........

    I think we MAY have this DSB thing wrong !!!
     
  13. Slagter

    Slagter MASA Contributor

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    This is the way that my DSB is run, except that the water level over mine is around 1 - 2 cm above the sand. And to be honest, it doesn't work for me at all. But I think that is because of the ass that designed my system.

    The water above the DSB, if running too fast blows the sand over into my return chamber. If too slow, the water level in my display drops. Purely because I don't have a proper overflow from my DT. Well, it's not an overflow at all because there are slits in the overflow box, towards the bottom of my overflow chamber. I don't know if that makes any sense to you, but ja...

    I recon the remote DSB is probably the better idea, but then it needs to be massive. I disagree that it needs to be really deep though. You just need 15 - 20cm of sand. With 3 - 5 cm water level above the DSB... If I had enough space where my tank is currently situated, I'd go remote DSB in a heartbeat, and replace my DSB area in the sump with a proper sized Scrubber and some reactors.
     
  14. RiaanP

    RiaanP Moderator

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    Something like this.

    [​IMG]

    The trick will be the height of the bottom pane, to force "good shallow laminar" flow. Basically to force flow over the sand instead of over the top. Too high, and you do not get the result. Too low, and you could end p sucking sand up. But I think 50mm cold be ok, need to play with it. Problem is that the answer will only show, once the sump is completely build. :(

    By the time the water reach the end of the DSB, I doubt if the laminar flow will be important anymore, so you need to skim the compartment with a over the top glass partition.
     
  15. RiaanP

    RiaanP Moderator

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    sorry, water level, 10mm below the top end of baffles glass.
     
  16. dallasg

    dallasg Moderator MASA Contributor

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    well there are SSB and DSB... the depth of the sand just adds to the effectiveness of the anaerobic area, the deeper the more effective it can be as there is a larger anoxic area.

    yes i agree that most DSB in the sump are combination fuges and DSB's for space, but that does affect the usefulness of the dsb
     
  17. RiaanP

    RiaanP Moderator

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    o, yes. another plus, if you got your cheato above the DSB, the slot idea will force water flow in between the DSB and cheato ball, not over and around.

    So yes, you can still combine the refugium and DSB. Or have them totally seperate.

    I'm keeping my tube anemones in my DSB. Nice place for them to be away from other corals. Tube anemone in DSB - Marine Aquariums of South Africa
     
  18. dallasg

    dallasg Moderator MASA Contributor

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    while they can be combined, i feel there is a substantial loss in the effectiveness of the DSB. this i am going to see on my new system by having everything separate
     
  19. RiaanP

    RiaanP Moderator

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    yes Dallas, agreed. Mine is split. I just did not like the cheato ball smothering (in my opinion) the DSB.

    And the DSB looks better, now with cheato removed. No more cayno and other algae strands due to the strong lights. Also easier to see excess detritus settlement areas on the sand.

    Do still have a small PL sump light fitting just for viewing pleasure.
     
  20. Neil H

    Neil H Thread Starter Moderator MASA Contributor

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    Thanks Riaan, i now see what you were describing

    nothing so far is telling me that my thoughts are incorrect
     
  21. RiaanP

    RiaanP Moderator

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    just to ensure I understand you correctly.

    You want to ensure that all the new water that enters the DSB chamber, gets contact time as soon as possible with the sand.

    With high water volume above the sand, it seems as it is not the case. And surely bubbles on the water just wash over the top to return chamber very fast, thereby giving the sense that the water just runs over the top of the chamber.

    I actually do doubt it as well, I believe if you take non toxic food colourrant, and inject it slowly from right in front of the first partition, so that it can follow the flow. You would be surprice to see the real water flow. I doubt if it is linear.

    When I feed the tube worm flakes, some small pieces are normally missed my its tentacles. I then keep an eye on what happens to the smaller missed pieces. And surely, those on the surface, goes directly to the return chamber, as the air bubbles. Those that is within 30mm from the surface floats to the end, makes a big drop downwards and floats back to the start of the DSB just above the sand, rise up again to continue their circular path until they are are trapped by the tube anemone, lands on the sand or goes over to the return.

    So looking at that big circular movement, I cannot see how the water 10 to 30 mm above the sand can be any more oxygen starved that the water 10 to 30mm from the surface.
     
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