Tunze Osmolator 3155

Most popular ATO system, most reliable and best in show!

It's no surprise Tunze makes the best ATO system you can buy. The dual sensor approach and internal timer helps to eliminate the most common failures, it includes a pump and is adjustable for efficient filling based on your tank size. The Osmolator 3155 is also the preferred ATO system by BRS employees with over 50 units in operation around our offices.

Innovative Marine HydroFill Titanium

Most econimcal without pump

This is the second generation of ATO systems from Innovative Marine and at only $70 the HydroFill Ti is the best priced option that does not include a pump. It uses reliable conductivity based sensors with titanium electrodes that are magnetically mounted for easy installation in tight spaces and all-in-one tanks. The ability to choose your own pump gives you the flexibility to use a water pump you already have and choose the right fill rate for your tank.

Tunze Osmolator Nano 3152

Best priced plug-n-play ATO

For a no frills complete ATO kit that includes everything you need, Tunze hits the mark again with their Nano Osmolator. In this case, they eliminate the optical sensor found on the Osmolator 3155 and rely soley on a protected float switch for sensing water level which is great for tanks up to 50 gallons. Outside of that, it is identical to Tunze's best selling ATO including the strong magnetic mount, dc powered metering pump and advanced controller.

XP Aqua Duetto

Best choice for tight spaces

This unit relies on dual optical sensors mounted inside a single magnetic holder roughly the same diameter as a penny. This means it will easily fit into the tiniest pump chambers and being a complete kit, it includes a small DC pump as well as a smart controller with built in logic to protect you against overfill and dry run.

AutoAqua SMART AWC Auto Water Changer and ATO

Best feature rich ATO - dual function!

Being so powerful, we could not pass up the opportunity to mention the AWC which not only functions as an automatic top off but also performs automatic water changes. It includes three pumps alongside the smart controller that will automatically remove and replace saltwater as well as replenish your tank with freshwater that is lost due to evaporation.

Tunze Water Valve with Osmolator 3155

Safest option for direct connection to RO/DI system

This is one of those options best reserved for the pros and larger tanks because you are connecting an endless supply of freshwater directly to your tank. The selenoid controlled water valve replaces the pump included with the Osmolator 3155 and then connects inline between your RO/DI system and tank. The selenoid will then open and close based on water level inside your aquarium allowing for a direct freshwater refill from your RO/DI system.