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Thread: Return pump size for 6 foot tank

  1. #1

    Default Return pump size for 6 foot tank

    I'm setting up a 6 foot biotope, replicating a fast flowing stream. The tank is 6 feet long and drains into an external sump. Currently looking for a good return pump that is also strong enough to deliver a reasonable, uni-directional current, like said fast-flowing stream. For reference, I tested out a 2000l/h pump as the return pump and only deliver a soft, calm current back into the tank. Right now I'm eyeing two pumps: a 3000l/h and 5000l/h.

    Which would be the better option?

  2. #2

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    You need to measure the head height from the return pump (in the sump) to the top of the display tank. Then look for pumps that do x litres per hour at that height. Most pumps do less than stated on the box and the higher the head height, the less water they pump up.

    Get a pump that does more than you need, and if you have too much water flow in the tank, fit a T-piece and tap in the return pipe to bleed some excess water back into the sump.

    Most marine tanks with sumps use a return pump for the sump to tank, and a couple of power heads or wave makers in the actual tank. They have the wave makers on timers. You can also have solenoids on the return pipe and have different outlets come on and off throughout the day.

  3. #3
    Join Date
    Jun 2013
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    ACT
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    Look up river manifold setups. 6 foot will be a big project requiring a massive pump potentially.

  4. #4

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    Quote Originally Posted by Colin_T View Post
    You need to measure the head height from the return pump (in the sump) to the top of the display tank. Then look for pumps that do x litres per hour at that height. Most pumps do less than stated on the box and the higher the head height, the less water they pump up.

    Get a pump that does more than you need, and if you have too much water flow in the tank, fit a T-piece and tap in the return pipe to bleed some excess water back into the sump.

    Most marine tanks with sumps use a return pump for the sump to tank, and a couple of power heads or wave makers in the actual tank. They have the wave makers on timers. You can also have solenoids on the return pipe and have different outlets come on and off throughout the day.
    From the bottom of the sump to the top of the tank measures 80cm. The 5000l/h pump pumps 3600l/h at 2m, while the 3000l/h pump pumps 2700l/h at 1.7m. Reckon I have a clear choice now. The reason I didn't use an additional wavemaker or powerhead within the tank is that it'll disrupt the uni-directional flow of the tank, which is what I'm after, so the flow in the whole tank will have to be provided by just the return pump.

    Quote Originally Posted by Rebel View Post
    Look up river manifold setups. 6 foot will be a big project requiring a massive pump potentially.
    I considered this, but it's too late now, because I've already drilled the tank . River manifolds are cool and all but more intrusive than just a sump.

  5. #5

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    Out of curiosity, what's going into the tank?

    Most freshwater fish don't naturally live in fast flowing water their entire lives. They might spend time swimming into strong currents as they head upstream, but they rest behind large rocks and in calmer pools before moving on.

    If you have lots of water movement in the tank, you need to make sure there are calm areas where the fish can rest without having to constantly swim into a current.

  6. #6

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    Native predator tank: Galaxias sp., Bostockia porosa and Tandanus bostocki. A biotope

    Species that are found in fast flowing areas, with dead zones provided by stones and wood, as I will provide. I’ll also make that T split and a control valve to adjust how much water is sent back into the tank by the return pump, and how much goes back into the sump.

  7. #7
    Join Date
    Nov 2016
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    Shepparton Vic
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    I have a 5000 lph return pump on my 4ft tank and it doesn't provide a fast flow.
    Have since added a canister filter to get more flow within the tank.(and help lift the crap off the sand)

    Think Rebel is right about the pump size, you may need to go big for the desired flow rates, or add a couple of power heads...

  8. #8

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    How big of a return pump?

  9. #9
    Join Date
    Nov 2016
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    Shepparton Vic
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    159

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    Not sure on how big, you may be limited by how much water can travel to the sump.

    Power heads might be a better option as you can add them or take away according to flow requirements.
    They are possibly cheaper?

  10. #10

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    Yikes, maybe I should’ve just done a regular old river manifold. Maybe I’ll add a secondary powerhead within the tank to give a bit of additional flow.

    I think my overflow can handle a fair bit of water. It’s a 50mm hole in the side of the tank.

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