Last Updated on April 24, 2023 by Coral Realm

Having an aquarium comes with numerous benefits, as you can read about in our article of the benefits of a home aquarium.

However aquariums also come with a far bit of cleaning and maintenance that you need to keep on top of. For instance cleaning the substrate and removing waste can be a nightmare without an aquarium vacuum cleaner. Another of these chores is making sure the water level hasn’t dropped and topping it up if it has. But with an auto top off system you don’t need to do it yourself!

In this guide and list we will explain how they work, how to install them, and the best 11 aquarium auto top off systems, finishing with our recommendation.


11 Best Aquarium Auto Top Off Systems for 2020 

What Actually Is An Aquarium Auto Top Off System?

As you may have noticed, due to the laws of nature water evaporates, and at higher temperatures water evaporates faster. So this means that the water in your aquarium will slowly decrease, and in a heated tank you will see this effect sooner.

Having a low water level in your aquarium is a serious problem. Your fish suddenly have less space to move around in, and this can cause fighting and health issues. It can also cause a build up of bacteria and detritus. Having the water level too low can also cause issues with HOB filters, especially if their intakes are near the surface. Not to mention the increased noise of water having to fall a distance to get to the tank!

When the water level gets low you need to fill it back up, and this means constant trips with the bucket, and cleaning up when you inevitably spill plenty on the floor. Don’t pretend like you don’t get any all over the sides!

With an aquarium auto top off system you are saved all this hassle, and your fish and plants are saved from having to live in a tank with a low water level. So it’s a win-win situation.

An aquarium auto top off system has sensors in place which keep a constant watch on the water level in your tank, and when it drops below a certain level it will give the water a boost and bring it back to the correct level. It also stabilizes the salinity and keeps the pump from drying up.

It goes without saying that having an aquarium auto top off system is extremely useful when you go away on vacation. You can be safe in the knowledge that the optimal water level will be maintained, so your fish and plants are being kept in the perfect environment. You will also be able to enjoy your tank without the worry of topping it up.

11 Best Aquarium Auto Top Off System Reviews

11 Best Aquarium Auto Top Off System Reviews

With many great models to choose from it can be quite overwhelming to try and pick one that is most suitable for your tank. Here we list and review the 11 best aquarium auto top off systems you can get at the moment. 

1. Tunze 3152.000 Aquarium Auto Top Off System Nano Osmolator

Tunze has a great reputation in aquarist circles. They have been manufacturing aquarium auto top off systems since 1985 and are known for great quality and reliable products. This model is one of their top two selling auto top off systems.

This auto top off system is very energy efficient, running on an 11V power supply and also having a very low voltage pump. This will save you money long term on power. There is almost no sound from it when it is operational, so you won’t be disturbed.

Weighing less than two pounds and having dimensions of only 1.5 x 1.2 x 1 inches this model is very small. It is easily installed via a magnetic mounting which can be used on glass of up to ⅜ of an inch thick. It can either be installed directly on the aquarium glass edge, or can be attached to the cabinet filter.

It works using a mini optical infrared sensor which enables the system to determine the precise water level, so it knows when to fill up and when it leave it be.

There is a safety timer which shuts off the system after 1.8 or 3 minutes as set by the user, so you do not overfill the tank. This is also a reason as to why it can only be used in tanks up to 55 gallons.

There is a slight trade off with this unit being so slight though; it can only be used with tanks of 55 gallons or less. In bigger tanks it won’t be able to keep the water level to the optimum.

2. XP Aqua Duetto Dual-Sensor Complete Aquarium Auto Top Off System

This auto top off system by XP Aqua is the world’s smallest dual sensor system. With dual sensors you get two precise level sensors to give you the peace of mind you won’t get your tank overfilled. The maximum glass thickness this can be mounted on is ½ inch.

Installation is extremely easy, simply plug in to the mains and you are good to go. There is no programming or adjustments required, so once you are powered up you can leave the system to it. You also get the pump and everything you need for the setup included.

With intelligent QST programming there is even more overfill protection, and precise water level control. The sensors don’t need light to work, so don’t worry about leaving lights on.

There seem to be a couple of reviews which say the sensors malfunctioned and didn’t shut off the top off, but the good reviews vastly outweigh the bad. But keep in mind that if the sensors malfunction you may end up with a wet floor.

3. EptTech Marine Reef Aquarium Auto Top Off System

One of the great things about this aquarium auto top off system by EptTech is that everything you need for setup and installation is included. So you are supplied the hose, hose holder, the pump, controller, and power supply. 

Believe us when we say this is a blessing, as buying an auto top off system and realizing you don’t have a pump to run it is a complete pain.

With a magnetic suction cup it is very easy to attach to the side of the aquarium, and means you also have control over where the sensors are. Just ensure that the glass is clean and transparent, otherwise it could interfere with the sensor.

This model features auto feedback security technology. This is a built in safety feature which ensures real time protection from failures and malfunctions. 

There are two LED lights which warn of failures; a blue and a red light. The blue signifies that there has been a non filling period, and the red indicates that an overflow has occurred in the system. This ensures that you can have peace of mind and quickly check the product for malfunctions.

The instructions that come with the unit are a little hard to understand however, and the magnetic suction cup can wear down and expose the iron core, so be sure to keep an eye on it. 

But this is a very good, well built product, which has a compact design and will save you countless amounts of hassle!

4. Auto Aqua Smart Micro Aquarium Auto Top Off System

Auto Aqua Smart Micro Aquarium Auto Top Off System
  • Max wall thickness: 1/2 inch (12.7mm) ,Mounts to Most Clear, Tinted or Painted Surfaces
  • Everything you need is included ,Safely keep water & salinity levels (in Marine Aquariums) stable.No moving parts that can fail
  • The siphon break needs to be mounted higher than the water level . Pump needs to be 24" or less distance from height of water level in Aquarium.
  • LED's can cause the Micro Ato to have trouble detecting water level so dont mount sensor close to any bright light source including moon lights, When the alarm is activated check reservoir level, check for bubbles on sensor, move sensor to darker location in sump or aquarium.
  • If the alarm has been on for more than 4 minute please reset unit by unplugging and waiting 10 seconds to re plug it in.

With the sensor being the size of a one cent coin, this aquarium auto top off system by Auto Aqua is small but well made and is highly rated. The system has a size of 2.8 x 6.3 x 6.5 inches and has a weight of 12 ounces. You also get a two year warranty included.

This system is very easy to set up and install. It is ready to go and requires no programming. You get everything you need in the package including the power adapter, tubing, controller, sensor, and mount. The mounting is magnetic so simply attach it to the side of your tank.

The sensor works on an advanced technology called quick security technology. This technology works on a real time basis to provide protection against failure and over filling. 

This quick security technology enables the system to be reliable and functional. To change the optimal water level of your tank simply move the magnetic sensor on the side of your aquarium, and when the water drops below this set level the pump will activate and top up the water.

LED lights can interfere with the sensor, so try and keep the sensor out of the direct gaze of LED lights so you don’t have any issues. Remember that the siphon break needs to be mounted higher than the water level to function properly, and the pump needs to be 24 inches or less from the height of the water level in your aquarium.

Some reviews have said that the pump can be a little weak. If you have a small aquarium then you will be fine, but larger tanks may need a stronger pump to ensure this system can keep up with your needs.

5. XP Aqua Ultimate Complete 4-Sensor Aquarium Auto Top Off System

This is the second aquarium auto top off system by XP Aqua on this list and it is no mistake. This model is the world’s first four sensor ATO, which makes it unique in the market and gives you unrivaled functionality.

One sensor is utilized for top off detection, and determines the water level and when the pump needs to be activated. Two sensors provide a dual stage overfill alarm complete with intelligent QST programming which provides protection from overfilling of your tank. The final sensor is used for run dry protection, which is a first in the market. This provides protection from your reservoir running dry which can damage the pump.

These four sensors work in tandem to provide you with a highly precise water level control. 

Setup is very easy, simply plug in and go, all programming is already all done for you. However with versatile installation with accessories included you can also set it up how you wish. 

If you have a larger aquarium which needs a larger pump, a socket switch is included which can run a pump up to 10A. You also get a solenoid valve for aquariums which are topped off directly with an RO/DI system.

6. Digiten Aquarium Auto Top Off System

Digiten Aquarium Auto Top Off System
  • ◕‿ ◕💛 Simple, complete, Smart Automatic Top Off System, aquarium automatic water supply system, super easy installation and maintenance. Suitable for aquariums up to 5/8"(16mm) thick, durable PC material holder to prevent move, adjustable bracket on holder make different water levels possible.This auto water filler suitable for fish tank, statuary pond, aquarium, hydroponic.
  • ◕‿ ◕💜 Relay control, Smart ato System precise dual float water level sensor for overfilling protection. When the water goes below the minimum water level , the power will be activated, the pump automatically works, and cut off once the water level reach to maximum. The second float ball will work when the first float ball fails.This automatic water top off system will help you controll the water level reliabelly.
  • ◕‿ ◕🐠 Siphon break. The siphon break is optional installation part. It is recommended that the water level of display tank be higher than the reservoir, and DON’T leave the end of the water supply pipe in the water, otherwise, it will siphon after the pump shuts off, if so the siphon break must be installed at the end of the water supply pipe.
  • ◕‿ ◕❤️Plug-and-Play with all parts included. Auto Top Off System has everything you need is included, this auto top off system will also come with a pump and a ETL listed power adapter. Safely keep sump water levels stable, no moving parts that can fail.
  • ◕‿ ◕🍀 Our smart ato water controller system is suitable for all kinds of fish tanks, aquariums, sumps, hydroponics etc. Fish Tank Sump Water Filler Refiller`s the range of water level from aqurium sump top is 0-17cm or 0-6.7".Suitable for aquariums up to 5/8"(16mm) thick , save you a lot of time to enjoy your life. The Smart ATO Complete Kit will never make water overflow your tank, it is especially suitable for the sump with a lot of evaporation. 12 month warranty!

This auto top off system by Digiten is a great budget unit which will give you high functionality but won’t break the bank. It comes with a 12 month warranty as well which is great.

It is really easy to set up and install, and is suitable for tanks with glass up to ⅝ inch thick. The thick and durable PC plastic holder prevents slips, and the adjustable bracket enables you to set different water levels.

The dual float water level sensor provides precise water level identification and overfilling protection. When the water falls below the minimum level the pump is activated and cuts off once the maximum level has been reached. The second ball float acts when and if the first fails.

The siphon break is an optional extra at installation. The recommendation is that the water level of the display tank is higher than the water level of the reservoir. And do not leave the water supply hose in the water, as otherwise it will draw water back through after the water shuts off. The siphon break must be installed at the end of the outflow hose.

It is suitable for all kinds of aquariums and sumps, and comes with all parts you need for installation included. So simply follow the guidelines and get it started!

7. Tunze 3155.000 Osmolator Aquarium Automatic Top Off System 

As stated when they started off this list, Tunze have been manufacturing top off systems since 1985, and the 3155 auto top off system has been the number one in the world for a long time.

Having spent many years being the best at what they do, it’s not surprising to find that this auto top off system is reliable, well-made, and solid. It is a single compact unit which is very small at 3 pounds and measuring 4 x 1 x 2.5 inches.

It is very easy to set up, install, and get going with. It has a magnetic mount which is very easy and convenient to attach to the side of the tank. You don’t need to worry about any extra purchases, with this model coming complete with pump, power supply, and tubing. 

There are two sensors working to determine the water level. The primary sensor is a mini optical infrared sensor which provides highly accurate regulation and information. The secondary sensor is a floating sensor which acts as an independent backup sensor in the event that the primary sensor fails. 

These two sensors send accurate information to the system which will detect the water level dropping and pump water as needed.

This model is worthy of the reputation it holds. It is reliable, sturdy, and functions brilliantly. The only downside to this product is that the price tag matches the reputation! However it is well worth it, as you know you are getting a brilliant product.

8. Hydor Smart Level Controller Aquarium Auto Top Off System

Hydor Smart Level Controller, Automatic Top Off, ATO
  • 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
  • Insensitive To Surface Movements Of The Waves
  • Versitile. Can Be Used For Any Size Aquarium Or Sump. Adjustable Flow Rate Supply Pump Sold Seperately. Kindly refer user manual and instruction video for reference.

Hydor is another company with a great reputation for making great aquarium products, and this ATO system is no different. It low voltage and so won’t drain your electricity, and is designed to a very high standard and to resist rust in fresh and salt water, allowing it to be used in both marine and freshwater aquariums.

The smart sensor can detect the difference between wave action and an actual drop in water level, so the tank won’t be filled mistakenly and you won’t receive a notification. The smart level technology also reduces the problems related to lime scale deposits and bacterial film build up.

This model is equipped with a dual alarm system which features both light and sound, which will alert you if there is any malfunctioning within the system. 

It is ultra-compact at 5.5 x 1 x 2.5 inches, and is very easy to set up and install. A magnet suction cup is used to position the unit on aquarium glass up to 0.4 inches thick.This model will work on any size aquarium, however it does not come with a pump, so you need to purchase the appropriately sized pump yourself. 

The company feels so strongly about their product that you get a two year warranty with every model. And the customer service is very good, so if you have any issues simply contact them with your receipt and they will sort it out for you!

9. IceCap Dual Optical Aquarium Auto Top Off System

IceCap Dual Optical ATO - Auto Top Off Controller
  • Optical sensor may not operate properly in aquariums with high turbidity

This aquarium auto top off system by IceCap functions well to keep the water level in your tank at the optimum. It is all automated and is completely ready to go out of the box, so the setup and installation is very easy.

It monitors the water level via two optical sensors which track the water levels in the tank and the sump. The secondary sensor provides protection in real time from overfilling in case of malfunction of the primary sensor.

It will alert you if the sump starts to run low, so that you can top it up to ensure your aquarium is kept filled. 

A downside is that sometimes fish may cause the sensor to activate, and the LED light is very bright, so can be disturbing if it is in plain sight. The tubing that comes with this model may be kinked during shipping, so if it is soak it is warm water to detangle it all.

10. JBJ Aquarium Auto Top Off System Controller 

JBJ Automatic Top Off Water Level Controller for Aquarium
  • Equipped with two float sensors that activated with in seconds when your water level drops
  • Refills your sump or tank to reaches your set point
  • Electronic controller allows for two modes of operation with a total of three different set up scenarios
  • item package weight: 1.0 pounds

This auto top off system by JBJ has a number of great features, and JBJ is a company with a good reputation so you know you are getting a quality product.

There are two floating sensors which activate within seconds of sensing the water level drop. The two sensors and controller allow for two modes of operation with three different setup options depending on what suits your tank best.

One of these setup options allows you to pre-set a maximum water level, which is extremely useful.

The LED indicators mean you can easily read the system, as they are highly visible and easy to read. You will receive alert signals when the pump is operating, but these aren’t too loud so won’t be disturbing.

The main downside is that you need to purchase a pump for this unit yourself. However this does mean if you have a larger tank you can get a more powerful pump which will refill your tank.

11. XP Aqua Sumpless Aquarium Auto-Top-Off System 

The third and final aquarium auto top off system by XP Aqua on this list, this model is perfect if you don’t have a sump, as this has been designed specifically for sumpless aquariums.

The combination of the sleek overflow box and the innovative dual-optical sensor will help to keep your aquarium topped off and your water crystal clear. The dual optical sensors work in tandem with intelligent QST programming to provide precise water level detection, overfilling protection, and also a secondary fail-safe.

The overflow box is very easily installed using the magnetic mount which attaches simply to any aquarium. In a great extra feature, it acts as a surface skimmer to rid your aquarium water of any undesirable oily surface skim and also doubles as a media reactor for carbon, GFO or any media of your choice.

The whole system is very easily installed and all parts are included. So it is completely ready to go straight out of the box which is very good and saves time.

How Should You Choose An Aquarium Auto Top Off System?

best aquarium auto top off system

It is important to choose the right auto top off system for your aquarium, so how should you choose one? What should you base your decision on? Have a read through some of the following and keep them in your mind as you make your choice.


One which kind of goes without saying. Don’t get one you can’t afford! There are a real range of prices available. The cheaper options may have less functions but they will serve you just as well and will top up your tank without fault.

What is the setup and installation like? 

This is quite important, as unless you like getting hands on and spending time setting everything up and putting things together you’re going to want a model which allows you to be set up quickly and easily.

Many aquarium auto top off systems are ready to go right out of the box, and have a handy magnetic mounting so you just need to attach the sensor to the side of the tank.

Does it have everything included?

It can be a massive pain if you are pretty much good to go, and then realize that the model hasn’t come with a pump. If you already have a spare pump and hosing then don’t worry, and you can choose any one you wish. But an included pump is normally a bit of a life saver.

The complete package would have everything you need to complete the setup and be ready to install. It will have the sensors, the pump, any hosing you need, controller, and power adapter. We recommend getting a model which comes complete with all of these.

Aquarium Size

Have a look at what size tank the manufacturer recommends for there aquarium auto top off system. Some models will only cater for smaller tanks, as they may have a weaker pump, or a fail-safe which only allows a certain amount of water to be pumped at once.

If you have a larger tank just ensure you get a model which can handle a large tank, otherwise you might be left disappointed!

How To Install An Aquarium Auto Top Off System

How To Install An Aquarium Auto Top Off System

When you go to install your newly purchased auto top off system, always give the manufacturer’s instructions and guidelines through. Follow those as things may differ slightly between models, though most will follow this set up.

First things first, get everything out of the box and ready so you can see clearly what you are dealing with. Before putting anything in your tank, power it up and check that everything is working properly, trust us it’s a lot easier if you catch anything faulty now!

Next prepare your reservoir. This is the reservoir from which the system will pump water to refill your tank or sump tank. It can be anything you want, but we recommend having something with a cover and holes for the tubing to go through. Having a cover will reduce spills and also reduce evaporation from the reservoir.

Getting the sensors set up properly is the most important step, as this is what will tell the system when to pump water into your tank or sump. So make sure to read the manufacturers instructions carefully at this point. However if you have one sensor with your new system it will go into the tank or sump at the minimum water line, and when the water level falls below the sensor it will activate the pump.

If there are two or more sensors one or more will go into the tank and one may go into the reservoir as well, and then work in tandem to control the water levels. It can get a little confusing so again, read the guidelines!

When you’re done with the sensors install the pump. You want water going from the reservoir to the tank or sump, so you want the tubing from the reservoir going into the “in” outlet of the pump so it draws water from the reservoir. From the “out” outlet of the pump have the tubing going to the tank or sump you want refilling. Where possible try not to have the tube going underwater in the tank otherwise it can draw in water from your tank.

Once all that is done, plug in your newly installed aquarium top off system into the mains outlet and let it do its thing!


An aquarium auto top off system may not be an absolute necessity for your tank, but it saves a lot of time and hassle. You can relax and you can simply enjoy your tank without having to worry about the water level in your tank or sump. If you like the sound of this then also read our article on the 11 best automatic fish feeders.

Make sure you take your time in finding the right system for you and your tank, and with some of these units you can be shelling out quite a bit, so be sure to read the additional info on this page before you buy. It will give you a little more info and you will be able to see which one will be right for you.

As to which system we will recommend, we like the models by XP Aqua or Tunze. You are guaranteed a high quality product and you can be sure it will be money well spent. The XP Aqua Ultimate Complete 4-Sensor Aquarium Auto Top Off System is particularly good, with its unique four sensor setup.

XP Aqua Ultimate Complete 4-Sensor Aquarium Auto Top Off System

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