tunze osmolator
 

how much will the level vary with the controller between on and off cycles of the pump.

Depends on the size of ur tank, if it is a large tank the level wont vary at all, the IR sensor is really accurate. But sdince the pump will run for 10 seconds when it kicks on, in a smaller tank the level will fluctuate a bit, still negligible IMO

I run 2 of the regular units (not the nano ones)
With the newest models you can adjust the on-time (actually, it's probably voltage output) of the pump if you remove the unit from the case and use a phillips screwdriver

I have mine set to 250mL per shot
My sump level changes by 1/8"
My 20g QT changes by an amount I can't measure

In my sump I use both mounts. I have the 'eye' separate from the float and have adjusted the levels to be very sensitive

In my QT I use a single mount and the level is still very stable. We're talking less than 1/8"

HTH

As I said, and you most likely missed it as we posted together, you can adjust the newest models - the amount of water pumped per cycle that is