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Dual Optical Auto Top Off (ATO) Controller - IceCap


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Product Description

An Auto Top Off (ATO) system is notably one of the most important pieces of equipment for a saltwater aquarium and simply a must have for any reef keeper. The IceCap ATO monitors and replenishes evaporated water eliminating the daily task of adding water manually just to keep your aquariums water stable.


The IceCap ATO is a well thought out automated system with a fail-safe design that uses two (2) optical sensors to monitor the fluid level of your aquarium or sump. The second optical sensor provides real-time protection against failure of the first sensor. Best of all, it is very easy to install and contains no moving parts that can fail.


The IceCap ATO also alerts you when your top off reservoir gets dangerously low to prevent the water pump from running dry. A bright LED indicator will allow you to visually see the status of your IceCap ATO as well as any possible issues. 

Plug and Play

You simply move the magnet optical sensor base to the desired water level within your sump or aquarium. It’s that easy!

Mounts to Most Clear, Tinted or Painted Surfaces
Max wall thickness: 1/2 inch (12.7mm) 

Everything Included

Everything provided for installation and operation.


  • controller,
  • 2x optical sensors,
  • power adapter,
  • DC brushless pump capable of pumping to a height of ~6 feet and a maximum flow rate of ~74 gph and
  • 6.5' of water tubing with tubing holder. 

Will work in complete darkness!

Product Videos

What's In The Box? - 10 - Icecap Auto Top Off Controller 01:25

  • What's In The ...
  • IceCap Auto To...
    The IceCap ATO is a reliable dual optical sensor Auto Top Off ...

VIP Customer Reviews

Community Product Reviews

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  1. SO far so good

    Posted by John on Jul 17th 2017

    I am sure you wont be sorry you purchased this. So far, no problems. Never misses a beat.

  2. Very Reliable and a Great Value!

    Posted by Unknown on Apr 10th 2017

    This ATO is one of the best I've seen or used. It has two optical sensors. One to tell it when to run the pump if the water is low, and a second to turn the pump off it the first optical sensor would ever fail. Optical sensors are known for being very reliable as long as you wipe them off every so often (maybe once a month to be safe) to ensure there isn't salt or algae buildup. Having two optical sensors makes this one of the most reliable options out there and it blows away other options in this price point. I would honestly prefer this over the more expensive Tunze Osmolator since it has two optical sensors instead of one plus a float switch, which are prone to failure.

    There is an alarm that sounds (quite loudly) if the ATO resovior is running empty or if the backup sensor has triggered to turn off the pump to prevent overfilling. I've tested both alarms and they definitely work well. It comes with everything you need except the ATO resovior.

    The one thing I didn't know about this ATO that made me think it might be malfunctioning was that you need to have both sensors out of the water when powering up the unit. This calibrates the sensors. Once the pump starts up, you can lower the primary sensor to your desired water level. If you power on the unit with the sensor in the water it runs the pump until it hits the backup sensor... just a word of advice. I figured this out after contacting CoralVue support. They have been very helpful and quick to respond. Once I knew how to power it up properly I had absolutely zero issues and it had been very reliable and kept my salinity at a solid consistent level.

    I highly recommend this ATO to anyone! Just remember the proper way to power the unit on and it will be a reliable and wonderful ATO option for a great price!


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