I've used a Reef Fanatic dual level controller for 6 years. I cant even visually see the level change in the sump. People also like the units from autotopoff.com. The one that gets the most complaints is the JBJ since it needs a 1" level change. I like Aqualifters for topoff pumps. They are super cheap ($12), pump at a very slow rate, and pumping Kalk doesn't hurt them.