Second HOB Filter on order

After receiving a $20 Wal-Mart gift card ( ) from my grandmother for Christmas, I decided to spend it online and picked up a second HOB (hang-on-back) filter for the 28g tank.  It's currently running one Marineland Penguin 150 bio-wheel HOB filter intended for up to 30 gallons, so I figured it would be ideal to upgrade a bit.  A heavy fishload is just more appealing to people like me, and a heavier fishload means more filtration is necessary.  So I ordered a Whisper 10 (with a box of replacement cartridges) to be used in conjunction with the filter I already have. 

They (at the forums and in articles) say that the filter should cycle the amount of water in the tank 5-6 times an hour, minimally.  With my 28g tank came a 150gph (gallons per hour) marineland penguin bio-wheel filter, which is actually sufficient if my bio-load were lower.  (28 x 5 = 140 which is in the proper range.)  When I add the second filter, which circulates 90gph, the water will be filtered at 240gph.  This means the water will be circulated almost 9x in an hour with both filters, seeing as how the second filter increases filtration by 60%.   

And in case a few of you didn't know, I can't stand Wal-Mart.  Been boycotting them for years.  Might shop there once or twice a year, usually when I'm stranded in my hometown down south with nowhere else to shop.  But the money had already been spent.  What could I do? 

She meant well and I love her so much.

Just know, if not for receiving a gift card from family, I would not be ordering from or shopping at Wal-Mart, especially for my fishkeeping supplies.