01-29-2010, 02:40 AM
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Basically, there are two different philosophies for filtration: one that promotes high flow rate and one that promotes low flow rate. There are good arguments for both sides of the debate. Eheim basically builds their filters based on that second design philosophy. They generally have low flow rates and lots of space for media, which give the water lots of contact time with the media. For this reason, Eheim filters generally don't fit the standard flow rate calculations. It's always safe to be conservative for these kinds of things. Considering that using the "high flow rate" filtration philosophy, filter manufacturers recommend 5x turnover and I tend to go towards 10x per hour, I'd approach Eheim in the same way, but using their metric. So, if their filter was rated for 93 gallons, I'd probably think it's sufficient for half that.
More simply, if I were in your shoes and was going to heavily stock this tank, I'd probably get the next biggest size or, more likely, add a second filter. But I really like overfiltration.