I don’t know how I missed this advice: that the filter for a planted tank should turn over the water volume in the tank 10 times per hour. Are you freaking kidding me? I thought I was spending a decent chunk of change buying the Eheim Classsic 2213 filter which promised about 120 gph. But for my 40 gallon aquarium, that’s more like a total tank turnover rate of a paltry 3 times per hour. This whole planted tank gig is making me crazy. I try to do my homework, but I miss these key details. Then I get hugely frustrated. Honestly. Doesn’t anybody out there have some kind of simple flow chart or decision tree to help us newbies figure this stuff out? I’d have blown the bucks on a bigger filter if I’d known. I’ve been dabbling around with this hobby for well over a year, and I’m pretty frustrated to discover I’m still on a major learning curve. Couldn’t the fish store folks be a little more helpful when they see me coming? I own the mistake but, dudes, when I ask you if the filter will work on my 40-gallon tank, you could ask me a couple questions back.