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RE: Which Eheim to buy, Filter flow rates.

For years people have been buying filters based on advertised flow rate,
come up with general rules on how much flow you need for a tank with X
gallons of water, and follow those rules with success.  So if all filters
have the same percentage of flow lost due to the media added, we would just
be dupliacting our numbers and trying to figure out something new which
doesn't need figuring out.  Lets say we have a 20 gallon tank, so we would
need either a 120 gph filter (advertised rate) or XXXgph (actual rate), it
makes no difference unless we're trying to figure out exact details on the
tank.  My car has 210 horsepower, but only 150 at the wheels, so what, it's
still faster than a car rated at 170 horsepower because it uses the same
measurement.  All 1/4 pound burgers are the same size even though that's not
what it ends up wieghing after cooking, which doesn't matter unless you're
trying to measure exactly the weight of the food you're eating.


>an example, my Eheim 2217 is rated for 254 gph, or something like
>that, while
>the box states the actual flow rate with media is 112 gph.  Now, this is
>perfectly adequate for any tank the filter is recommended for, and actual
>experience backs this up:  Eheim filters do a fantastic job of
>cleaning out
>debris from the water, and keep it sparkling.  But don't make the
>mistake of
>comparing advertised rates of flow between one filter and another.  Those
>numbers are very deceptive, and can cause you to choose a filter based on
>phony information.  Not what you want to accomplish.