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JBJ ATO Automatic Top Off System Water Level Controller


Item #: JB5111

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Tired of lifting heavy buckets to refill sumps or tanks due to evaporation?

There is finally a professional grade product that automates refilling evaporated water. The All-New A.T.O. (Automatic Top Off) device is the most advanced water level controller system on the market. Lifting heavy buckets and spilling water is now a thing of the past. Maintaining stable salinity and specific gravity are no longer a problem since the A.T.O. will refill as soon as the water level drops. The A.T.O. will keep your reef tank parameters consistent, ensuring an optimal environment for your tank inhabitants.

Advanced Features

Float Sensors
The A.T.O. is equipped with (2) float sensors that activate within seconds when your water level drops and automatically refills your sump or tank until it reaches your desired set point. Each float sensor has been designed with an exterior guard preventing snails & hermit crabs from attaching to the sensors.

Electronic Controller Module
Our state-of-the-art electronic controller allows for (2) modes of operation with a total of (3) different set up scenarios, allowing you more choices for installation for your unique set up. Our compact controller also incorporates a visible LED panel + our innovative Audible Signal alerts when in operation mode.

Linkable Brackets
Your professional kit includes commercial grade "Linkable Brackets" that can easily be adjusted to meet your height requirements, and securely positions your float sensors. Many competing brands use inferior suction cups that are temporary that can lead to disastrous water spillage.

Pump Safety Protection
The A.T.O. automatically stops power to your return pump in you reservoir, in the event that your reservoir is low on water. This safety feature prevents pumps from running dry and failing.

  • Item: Water Level Controller System
  • Model: A.T.O.
  • Purpose: To automatically replenish water lost through evaporation
  • Power Supply for Pump Capacity: 2 Amps
  • Dimensions (L x W x H): 1.5" x 2.75" x 4"
  • Weight: 2 lbs
  • Water Pump: (Not Included)
Q: How large of a pump can I plug into the A.T.O.?
A: The A.T.O. receptacle will handle pumps up to 2 amp capacity.

Q: Can the Audible Alert be turned off?
A: Yes, it can be turned off if the "Speaker Buzzer" is removed from the circuit board.

Q: Why does my A.T.O. automatically shut off after a few minutes of operation even though the water level has not reached the float sensor?
A: All A.T.O. Controllers have a factory "Float Fail-Safe" duration time period of 3 minutes and 45 seconds of operation before power to the pump is turned off. The Pump LED will glow but power to the pump will not be turned on. This feature was designed to act as a safety mechanism in the unlikely event the float sensor(s) failed or if something was to get stuck in between the sensor(s). You will have to reset the float sensor(s) to restart the controller.

Q: Can I adjust the "Float Fail-Safe" duration time period?
A: Yes, the duration time can be extended to 14 minutes of operation. (Please see instructions below on adjustment.)

Manufacturer information

JBJ is a top-of-mind brand name in freshwater and saltwater aquarium supplies. The company is committed to innovation and manufacturing only the absolute highest quality equipment. JBJ’s philosophy is "to create products that provide extra value" to hobbyists. JBJ produces hundreds of aquarium products including lights, filters, heaters, UV sterilizers, wavemakers and top-off systems. The company is best known for their affordable line of Arctica chillers and the best-selling Nano Cube aquarium series. We carry the gamut of JBJ products and accessories and are happy to provide you free technical support while you’re setting up your new equipment.

4 Stars


Reviewed on
April 06, 2020

Yes, I would recommend this.

Three plus years So Far

Pros: Good price, reliable, easy to set up.

Cons: Must ensure floats stay clean.

i've been using this ATO for over 3 years, no issues. I've used different pumps, had it on 2 different systems, it has never failed. It's pretty basic and you do have to make sure the floats stay clean, which is the only reason i gave it 4 stars.

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Reviewed on
March 31, 2019

No, I would not recommend this.

Will not get a "float sensor" ATO ever again

Pros: cheap, convenient

Cons: Will eventually fail.

Some people say not to buy an ATO with float sensors. They say that float sensors will eventually fail - a snail will get stuck in one, it will get clogged up with algae, etc.

Those people are correct. Despite the all the failsafes that are built into this device, my JBJ overflowed onto carpet and wood floors - on three different occasions. I gave up. I've been topping off manually since then. I've heard that ATOs with other types of sensors are more reliable, but I also feed my fish & corals several times a day, & just top off then. My salinity doesn't change, and it costs nothing.

Was this review helpful? 4 0


Reviewed on
February 21, 2018

Yes, I would recommend this.

Great ATO, especially for the price

Pros: for the price its hard to beat. No proprietary pump, use what you like

Cons: Does not come with a pump, Must and I mean must maintain the float switch set up or the salt creep with interfere with their performance.

I have had my JBJ ATO for 8 years. I used it first on my solana 34, then migrated to my 60 cube. I sold the 60 and it went with it.

Was this review helpful? 1 0


Reviewed on
January 04, 2017

Yes, I would recommend this.

Goes on and on

Pros: Runs forever. Still works but replaced for age.

Cons: Maybe bigger than some.

Owned one for over 10 years and never failed. On top of that only used a 1 float design not two.

Was this review helpful? 1 0

mauricio canon

Reviewed on
August 04, 2016

No, I would not recommend this.

after a few years stop working

at the begining works great, then one day it doesn`t turn on again, one day i opened to discover that some humidity has damage the Electronic Circuit Board and now i have to refill water manually. it is too expensive for the poor construction that it has. to cost 79,99 at least must have a good water and humidity resistance but not.

Was this review helpful? 1 0

mark ramsey

Reviewed on
January 28, 2016

Yes, I would recommend this.


This is a great ATO. I wish I would have done it along time ago. I used to pour water into the tank that is 4 feet tall every morning from evaporation. Now I pour water into a 10 gal. tank on the floor every 10 days or so. I refer this ATO to my friends and folks at the fish stores, secretly of course.

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brian hancz

Reviewed on
January 25, 2016

Yes, I would recommend this.

Great until stopped working

This is a great design and worked very well for about a year. Then one day it stopped working entirely :( Not sure if I want to purchase the same unit or try another that might be more reliable

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Reviewed on
December 15, 2015

Yes, I would recommend this.

JBJ ATO System

This is the second JBJ ATO system that I am purchasing. The first one last 8 years and worked flawlessly. I think the microprocessor unit finally stopped working. It's so simple and very reliable. When you have a stocked reef tank, you only want simple and reliable components!!

Was this review helpful? 2 0

kenny haack

Reviewed on
December 04, 2014

Yes, I would recommend this.

great addition to my reef

This is a top notch product. I hate purchasing things for my reef as the current setup has served me well for 10 years. As everyone else I bought every bell and whistle I was told to and wasted so much money. My last ato was an old reef dose pump that worked like a champ for 10 plus years and I was sad to see it finally fail. This ato is great. You can use it in different configurations and itwill protect your pump from running dry. I like the floats and the cover around it to protect from invert interference. No suction cups is also nice. Any product still utilizing suction cups should be banned. There is an audible alarm but the way I am using it the alarm is out of the picture. You will like every aspect of this product.

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Reviewed on
September 04, 2014

Yes, I would recommend this.

Works good most of the time

This is one of the most useful pieces of equipment I have purchased for my system. I love not having to add water manually daily or twice a day. My one complaint is that sometimes it will allow too much water I evaporate before turning on and it causes the pump to run for a long period of time without filling the tank. I just have to restart the ATO and it works again.

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