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Hydor Smart Level Control Auto Top Off ATO


Item #: HD01043

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Hydor Smart Level Control - water level management system

Smart Level is the new versatile fully electronic water level controller designed by Hydor. Smart Level safely and easily handles the aquarium and sump water level due to evaporation. Designed to be used in the many different conditions that exist in the marine and freshwater aquarium environment. Smart Level technology reduces the problems related to lime scale deposits, bacterial film, and wave action, which ensures the continuous, safe, and regular functioning of the Smart Level control.

For the SMART LEVEL Control, all types of pumps can be used, up to a maximum power of 50W. Choose a pump with a flow and head suitable for the type of use. Note that it is best to use a pump that tops off slowly within 10 minutes (maximum topping-off time).

Top-off pump required and sold separately.

Units now include a polarized socket and will accept a standard 2-prong plug.

Manufacturer information

Hydor has been producing a comprehensive range of equipment for aquariums and ponds since 1984 and offers the best in high-technology for the creation of a living ecosystem at home. The factory has developed thanks to the engineering competence of its founder and its continuous growth is based on the investment it has made in research and the development of innovative technical appliances. A competitive and dynamic structure of more than 150 employees regularly engages in the implementation of products which meet the demands of 50 nations and keep pace with the evolution of the world markets. The global quality is not a simple working method but a daily expression of mind.

4 Stars


Reviewed on
September 18, 2019

Yes, I would recommend this.

This is easy to set up and it works!

Pros: audible alarms, it works

Cons: sensor can be misaligned by bumping the cord.

have this set up in a 40gal breeder. my ATO sump is a 5 gal Home Depot bucket hidden in my home made cabinet. I clean the sensor about once every 4 months and it takes just a few seconds to clean off accumulated salt. the warning beeps are loud enough to get my attention across the room. I recommend this.

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Reviewed on
March 25, 2019

Yes, I would recommend this.

ATO on 46 bowfront

Pros: Auto shut-off, overfill alarm

Cons: Fixed distance and bulky sensor

I have had this ATO for about 6 months on my reef tank. The magnet+suction cup is great for keeping the sensor in place, but is somewhat bulky for a rimmed tank. It also does not prevent misalignment caused by anything knocking the cord, because the sensor can swivel. It is relatively easy to readjust by changing the angle of the sensor, and the 10 minute shutoff is great.

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Reviewed on
September 20, 2018

Yes, I would recommend this.

A good auto top off for a decent price and a reputable brand

Pros: Pros -No moving parts -Cheaper than most ATOs -Min and Max Sensor -Suction type cups have magnets built in

Cons: Cons -Does not come with pump -Slightest water level change can trigger alarm

I've had this product for about a year now and knowing Hydor being a good company that has been around for the longest time I bit the bullet and bought this unit. Chose this one for several reasons. Cost was much cheaper than most ATOs. Plug and play. And I know that Hydor's customer service is phenomenal. I've experienced their highest quality service when I did a warranty claim on my Koralias years back and I know I wouldn't have any problems getting help if needed. And their products are built to last. The only thing that would keep me from buying this product would be when the slightest water level rises due to your skimmer or water change or filter sock change the alarm goes off and this thing has the most annoying beeping sound. That's about it. Other than that I have not experienced any floods and any corrosion on the sensors. I'm using mine on my 135 gallon fish only with a Tom's aqua lift pump and it's doing the job. It's easy to move around. Magnetic suction type cups are super strong.

Final Thoughts: There's a reason that hydor has not updated this product for years. Because they build products built to last. What does differ this from other units is that the sensors are on one unit so you can't really change the difference between the sensors. This makes sense especially for smaller tanks being you don't want to have high salinity swings. If there would be one improvement to be made it would be to change how much sensitivity the sensors would have to water level changes so that the alarm wouldn't go off if your hand goes in the tank for example. And at least have hydor build or add some sort of top off pump so you don't have to buy it separate. Almost all auto top off units come with one these days.

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Reviewed on
January 24, 2017

Yes, I would recommend this.

Nice ATO

Pros: Consistency, audible alarms, LED indicators

Cons: Housing construction looks a bit cheap.

I've had this ATO installed alongside my 29g BioCube for almost two years, and it has worked great the entire time. I do appreciate the audible alarms to let me know if there are any issues with the ATO that require my attention. I'm using it with an Aqua Lifter pump and the combo is perfect for my needs.

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Reviewed on
December 30, 2016

No, I would not recommend this.

Not built to last

Pros: when working it is very consistent. easy to adjust.

Cons: low power output. need to match to your topoff needs by pump more than by device.

I used mine (and it worked very well) for about 10 months. It has since failed. Nothing changed, it just stopped working. It alarms at all times no matter what sensors are covered.

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peter frigola

Reviewed on
September 28, 2016

Yes, I would recommend this.

Hydor ATO

So far the ATO has worked flawlessly. I really like the display letting me know if we are on the Low side or high. Either way the audible alarm provides a warning.

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harold lane

Reviewed on
August 22, 2016

No, I would not recommend this.

Not Sending Water

I have had this for about three months. At first it worked very good. Now I am having a problem with the sensor tell it to send water into the tank. The pump is clean and each day I use a tooth brush to clean the sensors in the tank at water level. I have reset this and tested by moving the sensors about water to cause it to turn the flow on and it does not work. I am in no way calling the company knowing from many articles how they treat people. I have also read how many use four stars and the majority have problems. This means it is a shot in the dark to get a good one. Customer service is the main thing in our hobby. This company deals with volume and does not consider the customer. The system is sealed and looks like it should work well but there are too many problems to recommend it. I would not recommend it knowing many other good ATO systems out there.

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david heap

Reviewed on
May 27, 2016

No, I would not recommend this.

Too Slow to Switch off

Using this on a 25 gallon sump to top off my 135 reef, the sensor is too slow to react and tends to fill sump too fast, even with a super small little Desk Type water fountain pump that pumped maybe 1 gallon a minute. the submersible sensors need different vertical spacing to allow a lower dead-band of switching, or make the sensor thermalcouple be more timely to switch. I'm going to try it on a 40 gallon sump next. but right now it's gather expensive dust as a lesson learned.

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joseph barton

Reviewed on
March 22, 2016

No, I would not recommend this.

Failed Electrodes

Electrodes failed causing overflow of top off water. Didn't have it for that long. worked ok for a while but when the electrode failed the whole thing becomes useless.

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joseph ganja

Reviewed on
December 28, 2015

Yes, I would recommend this.


Now this is my first auto-top off unit and I must say for the price I am very impressed. It works very well and it's reliable. Hydor always delivers. The only thing that bugs me from time to time is that if the sensor isn't level to the water like if it's tilted just a bit it starts to beep until I get it right. But again I move my sensor quite a bit and its in a hard to reach place. With that said once you place the sensor and leave it alone you won't have any problems. Definitely worth the price. Much better than those more expensive auto top-off units.

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