Yea I'm not sure why either but I've tried it on a couple systems. Seemed like every other week it needed adjusting. Could have been build up on the foam pads, the needle valves, the return pump itself, or the gravity shifts from the moons placement. I wish it worked out for me though because I paid 350 for my feed pump but I cannot agree that it was a waste. CSS220 and aquamedic ato were a waste but this pump is nothing short of amazing.
To the op. I paid 350 but originally I got it for an auto water change system. It did great but I realized I really don't mind doing them manually. The second pump head was so I could reduce the rpm on the motor by 50%. My demand is crazy high and I was concerned about the tubings longevity. It was simply a precaution. 1 head works just fine. I already had it so decided to add it on recently. It ran great for a few years without it.
One reason I got the digital one was it would not restart after a power outage. This was great for the water change system but not so much for the reactor. I have it on a battery backup and so far it has been flawless. If I were to purchase one specificly for a reactor it would be one with a knob for speed adjust so it comes back on after power loss.