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Re: Which Eheim filter to buy

In a message dated 8/23/2000 00:57:21 Pacific Daylight Time, 
Aquatic-Plants-Owner at actwin_com writes:

>     The Eheim catalog shows The #2222 as having "pump output" of "apprx." 
>  liters/hour, and "filter circulation" of "apprx."  350 L/hr.  I don't know 
> if 
>  that second figure implies that the canister is charged with recommended 
>  quantities of Eheim media, or empty.  I've been assuming that it means 
>  the media.  The numbers for the #2224 are "apprx."  700, and 500 L/hr., 
>  respectively.
Careful.  The flow rate numbers published by filter manufacturers are rated 
with an empty filter, no media, at zero head (no water lift).  In the real 
world, the actual flow rate drops significantly, as much as 75% with some 
brands and models of filters.  Eheim does give you credible rates with media, 
but those numbers are printed on the box, not in catalog advertisements.  As 
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.