05-06-2010, 01:39 AM
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Eheims aren't "high flow"filters. Filter statements about flow rates are exaggerations but they are deceptive. Canisters are tested, empty with no hoses, so the flow rate obviously is going to be substantially higher than a canister filled with media, 4 months old, and a rise on the tube of 3 /12 feet.
The test empty so companies can't "smudge" the evidence. Different companies have different media, in differing amounts, with different tube sizes, with different rises to the aquarium by the hobbyist. To maintain uniformity, the filters are tested empty on a table.
You may not want a high flow rate, for example, planted tank issues, UV sterilizer issues. A lower flow rate with a decent UV sterilizer will kill ich in the water when it goes through its water born stage, too high a flow rate and the ich won't be killed. There's more to filtration than flow rate.