I will speak only from my experience with this product. I bought one several months back (perhaps 4-6 months ago). The package had been previously opened and as it turned out an integral part was missing. I improvised and was able to get the ph to work correctly for a couple months.
After it quit I called Zoomed and explained my situation and convinced them to send me replacement parts free of charge. It has worked well since(occasionally it stops sweeping) - sometimes requiring a cleaning, sometimes just turning the power on and off several times to dislodge whatever has gotten stuck in it.
I love the random currents it provides in my 46gal bowfront. Yes I do have to fidget with it now and then, but for $40 or so that I paid (as opposed to $$$$hundreds for other wavemaker devices) it works for me.
I have not used the prefilter sponge, so I don't know if that would make any difference. Basically any very small particle can get lodged in the flywheel which will stop the gear in the rotator outlet to stop. Additionally buildup of calcium can cause the same issue. I have had success with taking it apart and scrubbing it down witha toothbrush, and I now have an extra flywheel I can swap out.
These ph have gotten a bad rap from a lot of reefers, so you must take that into account. But again, for me, in my current tank and for the $$ it has done what I wanted it to do (my leather toadstool has never looked better either due to the random water motion in the tank)
HTH :wink: