I bought a Tunze Osmolator nano for my 45 gallon cube. I was afraid of the same thing but with this one you can set it and either at 2 or 5 min and if it the float hasn't stopped it it will automatically stop and won't run again until you in plug it and it resets. Even at five min the pump it comes with is small so its less than half a gallon it flows.
Now that sounds like a good deal. I will have to check it out. How's your tank doing?? Mine is filled to the brim. I'm looking at upgrading to a 180