Reef Breeders Exo-ATO

(62 customer reviews)


The Reef Breeders Exo-ATO is super compact and ultra-intelligent. It works great for maintaining your water level in aquarium sumps small and large.

352 in stock (can be backordered)

Warranty Period

SKU: exoato Category:


The Reef Breeders Exo-ATO (External ATO) is one of the first ATO systems to contain all electronics outside of your aquarium. The controller and sensor mount to the outside of the glass, and a small magnetic ring is inserted at your desired water level. That leaves only a 1/2″ thick x 1″ diameter ring inside your sump, so it will fit easily in clear acrylic or glass sumps!

Fully Self-Contained.

The Reef Breeders Exo-ATO is fully self-contained, meaning the controller, sensor, and backup functions are all contained in one small central unit. There is one plug for power in, and another plug for power out to the pump (included). That’s it. No more controllers to mount in your aquarium stand, and no more obtrusive sensors in your sump!

Intelligent. Redundant.

Every Exo-ATO has a computer onboard with several built in safety features which are listed below:

  • Frequency Alert: The system will beep to notify you that your aquarium has not been topped off for an unusual amount of time, at least 24 hours and double the average time between Top Off. Ex: if the Avg. time between topping of is 12 hours, the system will notify you after 24 hours of not topping off.
  • Overfill Alert: The system develops and average time that the pump is running each time the system is activated. If the system detects that liquid has been dispensed for more than 3x that average baseline time, it will shut the pump off and create an audible alarm.
  • Empty Reservoir Alert: The system can detect when the top off pump is drawing excess air/running dry and automatically shut the pump off and create and audible alarm.
  • Sensor Obstruction Alert: The system will detect if the in-tank sensor needs to be cleaned, is being obstructed, or is out of alignment. This is denoted by a flashing blue light.

All Inclusive.

The Reef Breeders Exo-ATO includes everything you need to get started- Just add water! The Exo-Ato system includes the sensor/magnet lens pair, a small dc power supply, a pump, tubing, and a tubing holder that fits most sump trims. They can also be used in the return chamber of all in one aquariums 20g or larger. Designed for clear glass or acrylic up to 0.20 inches (5mm) in thickness.

Every Reef Breeders Exo-ATO includes a full 12 month USA warranty.

Ships from Wakefield, RI USA

Additional information

Weight .85 lbs
Dimensions 7.25 × 5.5 × 2.75 in
Included Accessories

60" Tubing, Manual, Power Supply, Pump

Product Dimensions

1.4" Diameter, .6" In Tank 1.75" Diameter, 1.25" Outside Tank

Maximum Glass Thickness

Clear Glass or Clear Acrylic Only, Up to .20” or 5mm

Ideal Tank Size/Type

25 gallons and up, In Sump, Not Designed for use in display tank

Safety Features

Audible Alarm, Intelligent Timer Built In, IR Visual Level Sensor

Maximum Head Height

8 Feet

62 reviews for Reef Breeders Exo-ATO

  1. mark hall (verified owner)

  2. William (verified owner)

    Pretty simple to install and has worked perfectly since day one!

  3. David O. (verified owner)

    Easy to set up and has worked flawlessly. Excellent product for the cost!

  4. Chris Maynard

    Out of the box this is a 5 star unit taking into consideration price, ease of set up. Its only been set up for a short time so time will tell me more about its reliability but the pump kicks on a expected, it is far more powerful than you would think for the pump size. The pkg say it has 6.9 ft head capability, and i am running it at about half of that without issue. Well worth the $$$

  5. Anonymous (verified owner)

  6. Dave (verified owner)

    Great ATO. Setup in 5 minutes and just works.

  7. Aaron (verified owner)

    It’s my first ato. Very easy to use and working well so far.

  8. Vincent Manfredi (verified owner)

  9. Joe POMEROY (verified owner)

    Great product. Sets up in minutes. Works great

  10. Joshua (verified owner)

    AWESOME. The ATO is simple to use, simple to setup and has all the smart features I could ask for. All at an affordable price. And I can’t say enough about the customer service. Reefbreeders is by far the best CS I have dealt with in the last several years. I am thoroughly impressed all the way around.
    Great products.
    Great support.
    Great prices.

  11. Mike Lachance (verified owner)

    Very good ato, great price

  12. Vickie S. (verified owner)

  13. Lee slinkard (verified owner)

  14. Robert (verified owner)

    Always a wonderful experience with Reefbreeders products and service

  15. Mooresteven923 (verified owner)

    1st time ordering from reef breeders had a great experience. Ato is doing its job I got no complaints.

  16. Kyle C. (verified owner)

    Best customer service there is! And the products are top of the line

  17. david w. (verified owner)

    Very easy to set up, only minor issue is the sensor slipping out of alignment though that seems to have stopped.

  18. Erik (verified owner)

    Very happy with the product. Easy to set up, been working great!

  19. William Bowers (verified owner)

    I really like this ato. I literally had it up and running in under 5 minutes. Very little footprint. I’m very happy with my purchase and definitely recommend this product

  20. Jeff

    Product works really good and keeps water level steady. Only faults I have with it is it the alarm is quite. Inside a cabinet with other equipment running you can barely hear it alarming. Also, the only way to reset an alarm is to unplug it and plug it in. A simple reset button would have been nice like on their other models

  21. james spinnato (verified owner)

    Great ATO LOVE IT LOVE IT!!!!!!!!

  22. Jorin (verified owner)

    This is a great all around ATO for nearly any system. Just make sure it is straight and is maintained in alignment with the optical sensor as well.

  23. Mark S. (verified owner)

    First, Logan is awesome with his quick responses. The product works as advertised I have no complaints at all. The size of the pump is perfect and powerful.

  24. Hank Mirsky (verified owner)

  25. Dalton A. (verified owner)

  26. Stuart Barickman (verified owner)

    I am a little nervous about this product. I have it set up as instructed and have had 2 separate times where I’ve had to manually put water in my tank because my ATO wasn’t reading the water level. I’m about to leave my house for 2 weeks and hope to get this dialed in before then

    • Logan Vanghele (store manager)

      Hey Stuart, you are welcome to reach out to us to get this dialed in! They work ideally with thinner glass, so they are best suited for in-sump use, with a top off chamber at least 6″ x 6″ so the sensor has time to detect the water level change once the pump is activated.

  27. Chuck Annicelli (verified owner)

    Prior to ordering this one I had purchased a fancy brand name Auto top off that cost 3 times more than I paid for the Reef Breeders. I spent some time figuring it out and setting it up on my tank and then I realized the float will not fit in my sump. So I ordered the reef breeders unit and it was at my house within 48hours of ordering it. Between opening the package and installing it on my tank it literally took about 5 minutes to set up. This this is probably the biggest bang for the buck equipment that I’ve purchased. The amount of time I have saved in just the first week of owning it, not having to top off my tank two or three times a day makes it worth it. So far it has worked flawlessly! Great product!

  28. Tyler Martin (verified owner)

    Excellent product highly recommend

  29. kyle curry (verified owner)

    I have three and wouldn’t buy anything else

  30. Chad M. (verified owner)

    Only had it for a week so far but love it. It’s compact, quite and the easiest one I’ve ever installed.

  31. Erik L. (verified owner)

  32. Edward (verified owner)

    The ATO and service from Logan is top notch!!!

  33. Mark (verified owner)

    Very simple setup and just works as advertised. Only used three days but flawless so far.

  34. George Willings (verified owner)

    Easy to setup and easy to use. Works as advertised. This far very pleased with the product.

  35. Colin G. (verified owner)

    I emailed a question on a Saturday and Logan responded within minutes. Terrific customer service! The ATO was super easy to install and appears to work as it should. Overall a great experience with Reef Breeders!

  36. Nathan (verified owner)

    Received ATO in a timely manner, one of the power cords was the wrong size, contacted the company and they promptly advised they would ship a new one.

  37. John W. (verified owner)

    Great product. Works well and looks sleek! Would suggest longer cords for routing.

  38. CHRISTOPHER HYMEL (verified owner)

    Small, lightweight. Pump can fit into an opening of probable 1.5 x 3 inches. Cannot comment on longevity yet. Tip: Don’t put it in a tank that needs to be topped off by a large amount initially. This will cause the unit to assume that the volume it fills the first time is your average fill volume and try to overfill the next time. Simple installation. Simple mistake and on me but it would be nice to add to documentation on how to reset the memory of the controller to reset the estimated fill volume, both in a case of an inital large fill or swapping tanks.

  39. James Smith (verified owner)

    Great product, fast shipping. Thanks!!

  40. Carter Macdonald (verified owner)

  41. Scott (verified owner)

    Simple to install. Compact, sleek design.

  42. Dynelle (verified owner)

    Product works great and gives a clean look to cable management.

  43. Ryan Slade (verified owner)

    Amazing service fast delivery. Always first site I check for equipment

  44. Gary Hill (verified owner)

    Excellent ATO however I ordered the EXO and need the prism this will be a backup now

  45. Matthew Smoyer (verified owner)

  46. David Scarborough (verified owner)

    My order for the ATO was promptly processed and the device shipped the next morning. I had the box open and the ATO installed in 5 minutes and it has functioned as promised. Quiet, efficient and favorably priced. I highly recommend

  47. Edward Keppick (verified owner)

    No more constant checking my drip ATO. This unit is simple plug and play.

  48. Joe S. (verified owner)

    Great product designs. Easy to set up. Very happy

  49. Peter S. (verified owner)

  50. RICHARD GOLDSTEIN (verified owner)

  51. Jason Griggs (verified owner)

    Great product. Works like it should. Decent price. I’m going to buy 4 more of these before price goes up. Lol. 3 more for my tanks n a spare. Recommend this product.

  52. Mark (verified owner)

    The Exo-ATO sets up in minutes and just works. This unit keeps my topoff level perfect. BTW, I emailed ReefBreeders regarding the failure of a Prism ATO sensor under warranty that rusted out. In hours Logan returned my email informing me he would immediately replace the unit and I had it in my hands in 3 days. ReefBreeders customer service is excellent. I have purchased 2 RPM pumps, 2 QP7s, a Coral Box skimmer and a Photon 48 V2+. Great value, solid products and great customer service keep me coming back. Thanks Logan

  53. Tami (verified owner)

  54. Shaun Skursky (verified owner)

    This is an amazing ato….super easy to set up and works flawlessly

  55. Michael Gardner (verified owner)

    Great product!!!

  56. Joshua Lewis (verified owner)

    Great works ATO!! Price was great!!

  57. samuel d. (verified owner)

    Very nice unit. Works great right now.

  58. Fernando

    Reef Breeders is FANTASTIC. I was having issues with my previous ATO system. I contacted support, and after a few questions to understand my problem, they shipped me the EXO-ATO and it worked perfectly out do the box! I’m so happy I decided to shop here.

  59. Chris mims (verified owner)

    This is the best ATO. Its super reliable and the safety features make it accident proof. The only thing I do is occasional cleaning of the optical sensor wet side and investigate if the alarm goes off (which is not often if there are no environment changes). Great job reef breeders!

  60. Chris F. (verified owner)

  61. TJ Lysiak (verified owner)

    I have been in the industry for almost 20 years now and hands down this is the best ATO I have seen. Price is great, quality is amazing, and the pump is silent!

  62. Denise S. (verified owner)

    Timely and exactly what we needed

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