Personally I've had a whopping single problem in a year running a DIY'd (actually bear27 diy'd) weir style overflow. And that was my own stupidity, failed pump + failed top-off = big microbubbles problem.
If you do go with a CPR, get the one with the TOM aqualifter pump, 100% more reliable than a powerhead/venturi. Personally I'd avoid the U-Tube style as they have no ability to clear bubbles which could get into the tube.
Andy
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