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Re: [APD] Tank volume and Filter flow rate
If you don't want to actually time and measure the output
from a pump (or filter) then as a rule of thumb figure that
the output is about half the rated output. That's clsoe
enough, imo, for planted tank purposes. Rated outputs
usually are for completely unobstructed flow with no static
head. Filter media, biofilm tht develops in the thubing
walls and on the impeller and impeller housing -- all thise
things reduce the real flow.
Eheim generally gives two specs for filter output -- one
for the pump head alone and another for the filter with new
media (but again no tubing or such complications).
Unfortunately this apparent improvement in accuracy is
belies by the Eheim techniques -- eheim seems to always
rate larger canister filters with a higher output than
smaller ones in the same series even if they use the same
pump head and have a higher static head do to the larger
amount of media (the taller canister) the water must flow
through. The best explanation I ever got from Eheim for how
they conquered the laws of physics was that they use
different "tolerances" when rating the filters. Whatever
that means, it at least means that their measurements for
different size filters are not comensurable, imo.
Personally, I'd probably run two 2228s on a 600 liter
aquarium or else, maybe a 2250. But there's little science
in the hobby on what you *need* to have as opposed to the
different kinds of setups that can work. Many folks use
very little filtration at all, others try to get about 5
times the tank volume in hourly flow -- which, btw, once
you do the calculus, equates to a complete turnover of the
aquarium water 2 or 3 times a day.
A well planted aquarium is not nearly so fussy about
filtration as a nonplanted tank -- after all, plants are
good filters for nitrates and phosphates . . .
You would probably do fine with just the 2228 and a
powerhead for added circulation if you find you have some
stagnant areas in the aquarium. Running two filters gives
you the expensive advantage of only messing with half your
in-filter biofilter at a time.
Since you already have the 2224, you might try running that
pump on the CO2 reactor. If it's reasonably effective
reactor, that should be plenty of flow for that purpose.
Alternatively, you can stick to just one filter but clean
it more often as it will load and have its output reduced
more quickly than if you rune two.
But I'm sure you could have a great tank either way.
A good source for basic formulas on tank equipment, if you
are willing to make the simplifying assumptions necessary
to make the formulas at all practicable, can be found in
_Aquatic Systems Engineering: Devices and How They
Function_ by Pedro Ramon Escobal, Martin A., Jr. Moe
You can order it from most bookstores or get it at the
usual joints like this:
This covers aquarium water turnover rates, filtration,
skimmers (for those salties among you), UVs, etc. -- lots
of basic stuff.
Good luck, good fun,
--- Roger Thomas <sniper at home_net.my> wrote:
> I have a 5'(L) x 2.5(W) x 2'(H) tank. (650 litres to 700
> litres volume?) The glass thickness is about 1cm. I have
> a gravel thickness of 4 inches overall.
> I have 2 units of Eheim canister filters. These are the
> 2224, rated at 700 litres per hour (circulation 500
> litres per hour) and 2228, rated at 1050 litres per hour
> (circulation 750 litres per hour).
> Those two filters are housed inside the tank cabinet. The
> cabinet height is roughly 2 feet.
> Currently only one filter (2228) is running and the
> output goes into a CO2 reactor and back to the tank.
> Somehow I felt that the return is _too_weak.
> Is there any sort of calculation that I can do to
> determine whether I need to install the second (2224)
> filter or perhaps another 2228 ? Please advise.
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