The confusion caused by X volumn to describe flow

Discussion in 'Pumps and Waterflow' started by Bob the (reef)builder, 25 Jan 2011.

  1. Bob the (reef)builder

    Bob the (reef)builder

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    I so often find confusion on this topic.

    People quote that you need 60x volumn or 100x to successfully maintain sps etc.

    Its horribly misleading when one considers the different pumps we may use, especially in larger tanks.

    I have a 5000l system. On one side where most if the pumps are hidden I have 18500l of flow produced by a selection of pumps such as aquamedic 3500 or 6500. These are centrifugal based uplift pumps, not the newer technology flow or stream type prop pumps.

    These pumps producing 3.7x volumn:eek: keep the large SPS population in my tank very happy.

    On the other side, just to fill in a gap or two I have two 15000lph flow/stream pumps.

    You might think that the 30 000l produced by the flow pumps must be far more significant than the 18 500l on the other side. You would be very wrong. :tt2:

    Switch off the flow pumps and you will be hard pressed to notice, hell days have gone by before I've realised that these pumps had been turned off.

    Switch off the main flow of 18 500l and the tank goes dead. Only the tiniest flicker of life from the flow pumps tell you that the power hasn't tripped entirely.

    So how does something almost half the volumn of of the second massively eclipse the second.

    Simple. Energy. Assume that you put 22watts into a flow /prop/stream type pump designed to produce 15000lph. Maybe it is 95% efficient (ie 95% of the energy fed into it produces water flow) so nearly all of the 22w go into water movement.

    A 65watt centrifugal pump may also be 95% efficient but only be rated to produce 3500lhp. This one will make much more impact at churning water around, because the jet created moves the water around it as well, getting it all going.

    How? Simple. 65watts of energy is a lot more than 22watts. No matter how good German engineers are they have not found a way to produce more energy from a machine than is put in.;)

    Stream type pumps are great, they manage to move large volumns of water around without undue stress on corals placed quite close to them. This is why they were designed. The close proximity of everything in the average aquarium makes them very useful.

    But the way that they produce circulation is so different to other pumps that it leads to some confusion. X volumn becomes meaningless. Try comparing a CLS to stream pumps using x volumn for true meaningless information.

    We should rather use watts per liter if we want more acurate comparisons or ways to help each other regarding flow. :)
     
    Last edited: 25 Jan 2011
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  3. Manic

    Manic Moderator

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    The other difference come in water velocity exiting the pumps. Uplift pumps produce high velocity streams and "wave maker" style pumps produce low velocity water movement.
     
  4. 459b

    459b Moderator MASA Contributor

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    Positioning of pumps aso plays a crucial role in tank flow.

    Not sure if i agree with the watts/ltr measurement cause some pumps are way more energy efficient than others.
     
  5. Bob the (reef)builder

    Bob the (reef)builder Thread Starter

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    Absolutely, some pumps are more efficient than others. However the differences in efficiencies are minute compared to the total meaninglessness of comparing different classes of pumps using x volumn.

    We could use (Watts)(efficiency) / liter if you wanted better accuracy.;)
     
  6. Singularity

    Singularity Hmmm amper!

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    so now we dont want wide dispersed flow, we want a jet stream into the tank ? I thought the whole point to having flow pumps were to create a huge amount of water movement that doesnt rip everything to shreads ?
     
  7. SIMS

    SIMS

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    its all depends on distance. I have a 1800x1200x450 and have 2 Octopus 3000lph pumps that shoot jets of water. There are no corals close by and it gives me an awesome flow. I have 2 12000lph sun suns that I recon give no where near the same flow...basically saying the same thing as Bob :p
     
  8. Singularity

    Singularity Hmmm amper!

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    one question, if uou connect that pump to 50mm pipe as return (50mm into the tank aswell), will it still look like this pump is creating that much flow ? All i am saying is that everyone can buy those cheap powerheads as they create the same effect, for example you can have a 2000l/ph resun in a 1.2m tank and it will blow sand around at the other side of the tank as it bounces of the glass because the flow is "concentrated" through a 1cm hole.
     
  9. Adee

    Adee

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    I have a Hailea HX-6550 (5580LPH @ 200w) sitting on the bottom left hand corner of of my 2m x 1m. That pump alone creates a 'bow wave' on the entire length on the rim of the 1m wide pane on the opposite end. Would have been fine to leave that pump here had I intended to stay bare bottomed, I need to remove it though as I plan on adding sand.

    I will agree with Rob that the flow calculation many of us have used (including me) is not entirely true when trying to establish flow calculations for SPS requirements. As the types of pumps used would have bearing on calculation requirements. I reckon a couple of pumps with a high head out put to literally punch a jet of water through to the other end is needed (which I presume in Rob's calc would equate to the wattages used). This then would be something to look for. Downside is the size, wattage consumed vs head height, positioning and aesthetics to suite your preferences. The best part is I don't need to spend a fortune to install lots of the costly high tech stuff flow pumps to suite the SPS requirements, supplementing with "normal" pumps brings the cost down while at the same time keeping livestock all happy...just need to get pumps with high head height that use low wattages.

    I still would use a couple of Tunze's/Vortechs to create that random flow, to help challenge any dead spots from occurring.
     
  10. Bob the (reef)builder

    Bob the (reef)builder Thread Starter

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    No Singularity, you misunderstand completely. Stream pumps are great.

    What I am saying is that our usage of a x volumn way of discribing water flow in our tanks is rediculous when comparing different styles of pumps.

    If I had to put all stream type pumps in my tank I would use say 60x volumn to get decent flow for my SPS.

    Using the centrifugal style (uplift) pumps, I possibly only need 4-5x volumn for the same amount of actual water movement.

    This is a rediculous situation, how can we tell a newbee to use 60x circulation if he plans to use old-style powerheads or uplift type pumps, or a CLS. He will blow his tank to bits. However if he used stream type pumps this info would be perfect.

    The two different types of pump cannot use the same method (x volumn) to discribe flow its not compatible with both.:)
     
  11. Bob the (reef)builder

    Bob the (reef)builder Thread Starter

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    Both types of pumps are great at moving water. If you can get equally efficient pumps of both types, and you can. They do it in different ways and suit different situations.

    I am not comparing the two styles of pump, only saying that x volumn should not be used across both types.

    Watts put into the water (assuming efficiency) can be used as a valid way to express how much water movement is required, and can be used across both pump types.
     
    Last edited: 26 Jan 2011
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