Auto top off systems replenish the evaporated water that occurs in our reef tanks. Because evaporation only affects water and not the salt in the water, large salinity swings could have a detrimental effect on the tank. Also, if too much water gets evaporated, your return pumps may end up running dry and can lead to equipment failure. You’d need to manually pour fresh water into your tank every day to keep up w/ this balance. On my system, I’m losing several gallons a day due to evaporation (mainly due to my water movement and fans blowing across the surafce water to help w/ temperature). Topoff systems maintain this balance automatically!
Here’s how my auto topoff system is set up:
1. RO unit fills water storage tank (20g) and is turned off, via a solenoid (Reef Relief Automated Aquatic Top Off Controller) that is connected at the inlet of the RO unit and controlled by a float switch. I use Rubbermaid brute containers because they are food grade and will not leech out chemicals into the RO water.
2. Tunze Osmolator controls water level in the sump via optical water sensor. The Osmolator pump sits in the water storage container. As the Tunze replenishes water in the sump, solenoid opens and kick starts the RO unit to refill the water storage container. The solenoid controller is on a timer to prevent the RO from kicking on and off all the time (not good for water quality).
3. Periodically, I will pump fresh water from the storage tank into my salt water mixing container (10g). Water changes are generally done twice a week for a total of 20g per week or roughly 10% water volume.
