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RE: How much current is enough?

Hi James, thanks for the reply (more below)

>Gordon, I can vouch for the Eheim pumps rated for 1200 L/hr. I have 2 at
>opposite ends of my 130 Gal tank (72" long). They have turned the tank into
>a quickly flowing brook. To tell the truth, there is too much current,
>although most of the fish seem to love it. Some of the plants could do with
>a little less turbulence. I'm almost ready to totally re-do the tank, and
>they won't be part of the new set-up.

[Gordon] If (as Ivo suggests) my Powerhead is defective, this might give me a
opportunity to return the powerhead and swap it for a Eheim. I think the Eheim
would be better suited to using with my CO2 reactor then trying to create some
bodgy pipe apparatus to connect the powerhead to the reactor. How have you
placed the pumps in your tank? Are they located inside the tank or outside but
with pipes running into it? I have seen these pumps and they are rather large,
if I did replace my powerhead with a Eheim pump I would prefer to have it
located outside of the tank.

>Dupla recommended high circulation in The Optimum Aquarium, and to a point
>it is a vaild argument, but there is such a thing as too much of a good
>thing. Dupla recommends between 1-5 turnovers per hour (this is for
>circulation, not filtration). In Aquarium Ecology, a Supplementary Approach
>(a booklet put out by the German manufacturer Tunze), they recommend 1-4
>turnovers per hour in a freshwater tank (and 4 - 10 in a saltwater tank).
>Tunze goes further than Dupla in one aspect - they caution against the use
>of too strong a pump, which can cause "hard currents" (pumps which produce
>more than 2m of water column head). Shearing forces caused by such a strong
>flow could damage or kill planktonic micro-organisms (there is planktonic
>life in freshwater tanks too).

[Gordon] So it sounds like I do need circulation, the rate of circulation needed
though seems like a contentious issue.

>Rather than using one large pump to produce the desired circulation, it
>would be better to use two or more smaller units to ensure that although the
>circulation is through, it is not so violent anywhere in the system that it
>kills anything.

[Gordon] That sounds like smarter thinking, harder on the wallet but better for
the Aquarium.