The 6 Best Auto Top Off System Options For Your Tank

Alison Page

Alison Page


Best Auto Top Off System

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These days, more and more advanced technology and automation are appearing in the fish-keeping hobby. One of the most popular automation options is the top-off system.

Top-off systems are saltwater and freshwater aquarium accessories that work by replacing evaporated water in your fish tank, making this the ideal tool for maintaining water stability in your aquarium and giving you peace of mind.

Keep reading to learn more about how these aquarium products work, what to look for when choosing one, and to read our reviews of the best top-off systems currently on the market.

Best Auto Top-Off Systems

Tunze Osmolator 3155

Tunze 3155.000 Osmolator Auto Top Off System
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The Tunze Osmolator is made with high-quality material and is widely regarded as the gold standard auto top-off unit on the market today. 

The device features manual and digital sensors that work together to control and monitor your tank’s water level. The primary sensor is an infrared sensor, and the secondary sensor is a float sensor.

There’s an auto shut-off feature that prevents the pump from running for too long and rules out problems such as the aquarium overflowing if the switches fail. The unit has an audible alarm feature to alert you if the level of water becomes too high, and a high-quality Tunze pump is included.

Tunze is well-known for producing high-quality equipment that’s built to last, and this auto top-off system is no exception. These energy-efficient units last for many years and very rarely fail. In the unlikely event of a problem, Tunze supplies replacement parts, so you can keep your system running.

The main disadvantage of this auto top-off system is that it’s quite expensive. However, you do get what you pay for with this system. The Tunze unit is suitable for all aquarium types, including freshwater and reef aquariums.

What we like:

  • High-quality pump included
  • Digital and manual sensors
  • Auto shut-off feature

Room for improvement:

  • Expensive
  • Some users find the pump is quite loud

XP Aqua Dueletto ATO

XP Aqua Duetto Dual-Sensor Complete Aquarium
  • the Duetto is the perfect ATO for your aquarium
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The XP Aqua Dueletto ATO has been explicitly designed for ease of installation in all-in-one fish tanks and small-sized aquariums.

The system is marketed as the “world’s smallest dual-sensor aquarium top-off system.” Thanks to the fact that this compact unit doesn’t contain any moving parts and uses a digital smart sensor setup, the manufacturer has been able to create a very small device. The dual-sensor system acts as a safety feature and protection against failure of either sensor.

The pump supplied with the unit is a DC pump that uses less power and is also smaller. You can fit the pump into all-in-one chambers, where it still works effectively. The dual sensors work in total darkness, and because the sensors have magnetic mounts, they can be placed in the tank or the sump if you prefer.

You can use this device in a freshwater or saltwater tank.

What we like:

  • Small size makes the device suitable for use in all-in-one tanks
  • Excellent value, including pump

Room for improvement:

  • No auto shut-off feature
  • Only uses a digital sensor

JBJ Auto Top-Off

JBJ Automatic Top Off Water Level Controller for Aquarium
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The JBJ Auto Top-Off system is an excellent entry-level device for those on a tight budget.

Unlike many other top-off units, the JBJ system features dual float water level sensors that trigger the water level in the tank to rise immediately. This system doesn’t use digital sensors, but the design means that it’s not a problem. Its design allows for two modes of operation and multiple setup options.

The system is also customizable. You can modify the auto shut-off timing device, and you can switch on an alarm when the unit is activated. That’s an excellent control feature that provides protection from failures and can help prevent flooding should the float switches actually fail. 

The main downsides with this system are that you have to buy a pump with a power supply separately, and the mounting fixtures are not the best. You can choose a suction cup mounting option or bracket mounts that are not aesthetically pleasing.

What we like:

  • Affordable price
  • Easy to customize and modify
  • Auto shut-off feature protects against failure

Room for improvement:

  • No pump included
  • Mounts are not great

Hydor Smart Level Controller

Hydor Smart Level Controller, Automatic Top Off
  • Low Voltage And Fully Electronic. 6.5' Sensor Cord.
  • Dual Alarm With Light And Sound To Alert Any Malfunctioning
  • Magnet-suction cup support mount for sensor, also includes cable clamp for cord
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The Hydor Smart Level Controller uses a dual-sensor to manage your fish tank’s water level.

The sensors are situated on a single plug connected to the electronic controller, so the system is very easy to install. As this is a sump-based system, we recommend not using it in an aquarium. The design features a dual alarm system with sound and lights, and the sensors are not affected by water surface movement inside the tank.

Unfortunately, this system doesn’t have a pump, which you must purchase separately.

What we like:

  • Alarm 
  • Reasonably priced
  • Dual sensors

Room for improvement:

  • No pump included
  • No manual switch

IceCap Dual Optical ATO

IceCap Dual Optical ATO - Auto Top Off Controller
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The IceCap Dual Optical ATO device is a comprehensive system that includes dual digital sensors.

The sensors read the water level and provide a maximum and minimum sensor that ensures a backup for the unit. The unit comes complete with a good quality pump and magnetic suction cups. An alarm notifies you when your water reservoir is getting low, so you don’t need to look at the ATO container.

The main downside to this system is that it doesn’t have a manual switch and auto shut-off feature, but we think the unit offers good value for the price.

What we like:

  • Dual sensors
  • Reasonably priced

Room for improvement:

  • No manual switch


EPTTECH Aquarium Marine Reef Fish Tank Automatic
  • Package:Includes ATO Controller,Pump,90-250VAC Power Supply,1.8meters hose,hose holder and user manual;
  • Advantage:1.No cable in the fish tank 2.Magnetic installation
  • Function:Keep the water in almost the same level of the tank
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The EPPTECH system represents excellent value and has a very small footprint, primarily because the unit doesn’t have a float switch but has a digital primary sensor instead. That means the unit is small enough to fit anywhere in your fish tank, and the magnetic installation makes it easy to place.

The main drawback to this unit is that the quality control element of the production process is not great. Sometimes, the sensor fails, or corrosion damages the unit’s magnetic holder and optical elements.

What we like:

  • Small footprint
  • Excellent value

Room for improvement:

  • No backup sensor
  • Quality control issues

Do You Need An Auto Top-Off System?

If you’ve never heard of an auto top-off system, you’ll be wondering if you really need one. After all, your aquarium care includes carrying out partial water changes every week to keep the tank water fresh and clean, and you top up the levels in your tank at the same time.

Aquarium automatic top-off systems are an excellent tool for maintaining the stability of water conditions in any size aquarium setup. 

An auto top-off system keeps your salinity levels in your saltwater aquarium consistent and can also be used to add supplements to your aquarium environment via Kalkwasser. In a freshwater fish tank, using an auto top-off system can help maintain stable aquarium water levels to combat problems with evaporation, ensuring that your filtration equipment runs correctly and water levels remain topped up.

For the auto top-off system to correct a water level drop, you need a reservoir of water for the system to draw from. Depending on what system you choose, that reservoir could be the aquarium itself or the sump. You can also use a 5-gallon bucket or a spare empty tank.

Whatever form of reservoir you use, you’ll most likely need to refill it every five to seven days, especially if you have a larger tank size. That can save you the daily task of having to top up your fish tank manually and can greatly benefit you and your fish if you’re away from home.


Just like any piece of equipment in or out of your fish tank, you’ll need to keep the auto top-off unit clear of debris, bacterial film, sludge, and salt creep in a marine aquarium. If the unit becomes clogged with sludge, the switches could fail, and the tank will overflow.

So, once every couple of weeks, clean the unit carefully with a soft brush, paying particular attention to the switches. 

Auto Top-Off Systems – What To Look For

When shopping for an auto top-off system for your aquarium, there are a few additional features that you need to look out for.

Ideally, you’ll want a complete kit with the pump, hoses, controller, and power adapter.

Prices vary considerably, but you don’t necessarily need to spend a fortune, especially for fish keepers just starting out in the aquarium hobby. However, the following features are crucial in a good auto top-off system.

Fail Safes (Redundancy)

An effective fail-safe is the most important feature to look out for when choosing an auto top-off system for your fish tank.

Unfortunately, auto top-off failures are not uncommon, especially in units with a manual float switch. If the switch gets jammed and fails, the top-off system will not switch off, causing too much water to be added to the tank. So, ideally, you want an auto top-off system that features dual sensors, i.e., digital and manual.

Manual Switches

In the case of the manual sensor, you want a float switch. The float switch sits on the water in the fish tank. As the water level inside the aquarium rises, the switch activates, and you switch off the top-off unit. This type of switch is pretty reliable.

However, as the system contains moving parts, there’s always the danger that the switch will become clogged with algae or salt creep or become jammed with a wandering invertebrate. Sometimes, water movement can also cause the switch to fail.

Digital Sensors

If you choose a top-off unit with a digital sensor, you ideally want one that has an electronic eye sensor. The optical sensor monitors the water level in the fish tank. It automatically deactivates the top-off system when the eye senses water above the level at which it is set. Digital float sensors are generally reliable; however, they can eventually become clogged by particulates in the water. 

You’ll often see digital sensors marketed as having “no moving parts.” That’s the manufacturer’s way of telling you that these sensors are more reliable than manual switches.

However, both manual and digital sensors can fail, which is why you want to choose an auto top-off system that features a combo of both types of sensors connected to a self-leveling controller. That way, you always have a backup in case one sensor fails.

Auto Shut-Off Timers

Ideally, you want to choose an auto top-off system with an automatic shut-off feature. 

In the event of a switch failing, an auto top-off system with an auto shut-off feature will shut down the pump before flooding can happen. If the tank is overfilled, it can be disastrous for your home and for your aquarium, too. So, always try to choose a system that has auto shut-off capability.

Although you can make a DIY auto top-off system for your aquarium, that won’t have an auto shut-off feature incorporated into it, which could spell disaster if a switch fails.

Final Thoughts

If you’re out of town regularly or you live in a very warm climate where evaporating water is a problem for your fish or reef tank, you might benefit from using an auto top-off system.

An auto top-off system ensures that the water level in your aquarium remains constant, helping to keep water conditions stable and maintain aquarium health. These systems are very easy to set up and look after, with only minimal maintenance required to keep everything running smoothly. 

Ideally, aquarium enthusiasts want to choose an auto top-off system with an auto shut-off feature that will shut the unit down in the event of a malfunction, preventing accidents. Also, a system with both manual and digital sensors is less likely to fail than one with only a manual switch.

Did you choose one of the auto top-off systems we reviewed? Tell us in the comment box below. 

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