Review on Apera Instruments AI209 Value Series PH20 Waterproof pH Tester Kit: Unmatched ±0.1 pH Accuracy! by Lynn Woodcock

Replacing the motor helped eliminate a noticeable rattling noise that was mainly due to the original impeller shaft wearing out with the motor over the years. This replacement comes with a new stem and helps a lot. Having an old filter meant it still rattled a bit here and there, but rotating the motor unit (by turning the washer like a knob) to a position where it was quiet also helps to keep it quiet. as it supports the device slightly (actually slightly) at an angle. As with any old favorite that is built to last, sometimes you need to play around with them, play with them a bit, to get them to work 100%. Aquaclear filters, although relatively expensive for a hanging filter, are in my opinion the best on the market and well worth it.