I would like to start of buy saying I have been in the aquarium hobbies for over a decade and had always taken steps to reduce evaporation as much as reasonably possible. However after many years of topping off my tanks manually I decided to look in to an ATO, after reading many reviews and seeing a few videos I settled on this one and I'm glad I did. The ATO is very simple to to set up in just a few minutes. The sensor that goes inside of your aquarium is very small and the magnet used to secure it in place feels adequately strong enough that I'm not worried about it falling inside of my aquarium. I purchased a smallish 7 gallon water container one would use for camping to use as a reservoir for hold additional water and the small pump head fits very nicely inside. So far it has been working great. There is very and I mean very little noise heard from the pump when it kicks into action and the only time I've heard it was when everything in the room is shut off and its stone silent in the room. The only draw back that I can think that may throw some people off is the sensor it's self is a very very bright night light so best not to use in a bedroom I'd say if you like the dark that is but seeing as the aquariums in question are located in my home office / game room it doesn't bother my in the least. I have plugged my ATO into a smart plug to make water changes and gravel vacuuming easier as I can disable it while doing so. Hopefully people find this review helpful. 😊

Works great. The pump went out after several months and I replaced it with a $4 60 gallon per hour pump.

Make sure your homeowners insurance is paid up.

Purchased it awhile ago but never installed. Setup was quick and easy. Worked perfectly for two days then I came home to discover that it ran this afternoon but never shut off. It dumped the entire ATO reservoir into the tank. Luckily I did t trust it so the damage was limited to a gallon of water spilled on the second floor of my house. Now I am pulling up carpet and mixing an emergency batch of water to rescue my tank from the crash in salinity.

Not often that a product fails in a way that is destructive but going cheap may end up costing me thousands.

Works great! Simple and effective solution! Blinking light tells you it’s running!

Works as intended, and is great for the price. It only failed me once and of course it was while I was away for a week.

It lasted 2 years and the salt creep broke the seal on the optical sensor and water got in. Fried the sensor. But for $40, Id say it exceeded my expectations. I wouldnt use this on my big tank with expensive stuff, but a smaller tank is perfect!

I will just buy a replacement and maybe try to reinforce the seals on the new one. If only they sold the sensor separately

Really happy with this ATO system. It keeps the water level steady without any hassle, and it works great for both saltwater and freshwater tanks. Setup was simple, and once it’s running you don’t have to worry about topping off the tank all the time. A great upgrade for any aquarium setup.

This worked really well till it didn't. The sensor started giving out after about 2 months. It would start filling and just not stop. It would drain my entire 5 gallon bottle into my tank, which luckily isn't enough to send my 75 gallon tank overflowing... But it'll just sit there trying to pump water non stop when the sensor is very obviously fully covered in water. I've come out in the morning to my tank overfilled with the pump running air for who knows how long, likely at least 2 hours straight. The sensor was not dirty. I keep it clean. I have cleaned it after it's malfunctioned and it would malfunction again later that day. I have bought a replacement sensor from another brand. Somehow the water pump hasn't burnt out so I'm still using that. The replacement is working so far, but I've only had it about a week. I'm sure that while it's a different brand, they're all from the same manufacturer, because they're exactly the same. Hopefully this one lasts at least a little longer than 2 months... In that 2 months I became very much dependent on this system, I have pothos growing out of my tank, and when the water evaporates too far, the roots get exposed to air, dry out, then I top up, and those dry roots rot and die. Since having the system, that has stopped, and my plants are doing better than ever. I really need this system to keep working 😭

Maintaining the right water level in an aquarium is crucial, and this ATO makes it simple. Every aquarium loses water to evaporation, but in saltwater setups, that also means salinity levels start to climb. This system takes the guesswork out by automatically topping off the water, keeping both the level and salinity stable so fish and corals thrive.

The design is compact and sleek—just 0.7 inches in diameter—so it doesn’t take away from the beauty of the tank. Setup was straightforward, with all the parts included, and it fits perfectly in rimmed or rimless tanks.

I really appreciate the safety features. The QST protection gives peace of mind by monitoring refill times and preventing overfilling or pump damage if something goes wrong.

Overall, this is a practical, space-saving, and reliable solution for anyone with an aquarium. It’s not just convenient—it’s a must-have for maintaining a healthy aquatic environment.

Setting up a small reef tank in my living room, evaporation was disrupting my salinity stability, I'd lose 1-2 cups a day in summer. Picked up this ATO system and it's been running flawlessly for over a month now. It uses dual optical sensors, very accurate, no false triggers from waves or bubbles. When evaporation drops the level, the quiet submersible pump kicks in and slowly adds fresh RO/DI from my 5-gallon reservoir bucket (not included, but easy to connect with tubing). It adds the right amount in short bursts, keeping parameters steady, salinity holds at 1.025-1.026 without fluctuation. Installation was straightforward, mount the sensor bracket in the sump, drop the pump in the reservoir, route the tubing, plug in, and calibrate if needed. Pump is very quiet, no vibrations, and the whole system feels well-built for the with sturdy tubing and good connectors. No leaks after setup, highly recommend!

Ha funcionado muy bien

I bought this ATO for my nano saltwater aquarium and would not buy again. It failed twice in about 4-5 months. The magnet is not strong enough so any large turbo snail can push the sensor up, making the water level go up. Also, the glow of the light is annoying at night. Pay more money now for a good ATO with a strong magnet and a cover over the light sensor

Excelente producto muy buena precisión y fácil de instalar

Muy bueno el producto comple perfectamente con lo especificado