There are Tunze options for $$ or sub level $$$. Typically a sump will swallow up a good portion of RODI water if the unit is triggered to add water over the desired levels by dispersing through the entire system, so the 3155 by Tunze might be a viable option for you as it has the float switch to protect against this from happening.
More importantly is the placement in the display -should be away from any fluctuating water flow from wave pumps.
I not even set mine up yet so cant even give my experience lol.but here quick video from brs on most popular by viewers.3 times as many votes the winner got from others
Keep salinity and your aquariums water level consistent with Reef Breeders low profile Prism-ATO. Water level changes are registered in fractions of a second using infrared level sensors and with all internal components built into the sensor, there are no additional controllers to mount. Reef...