What is an ATO and Why do I Need One?

ATO or Auto Top Off is a device that helps automatically replace water that evaoprates from your aquarium.  This helps you maintain a stable salinity and specific gravity level.  ATO's help keep all salt levels at consistent parameters, ensuring an optimal environment for your tank inhabitants.  ATO's consist of a sensor that can detect water level changes (sometimes mechanical, optical and in combination), a pump, tubing and a container used to hold water.  Aquariums are constantly evaporating water, some faster and some slower, but they’re all doing it and they are all doing it all the time. When a saltwater aquarium evaporates water, the salts stay behind causing the specifric gravitly level or salinity of the aquarium to increase. Depending on the rate of evaporation, and the rate at which the evaporated water is topped off, the resulting salinity fluctuations can be a huge stressor for marine life often causing deaths.   This is known as osmotic shock, this stress factor can make the difference between a thriving and a struggling aquarium.