Tunze Osmolator Nano 3152 Auto Top Off Review

Tunze Osmolator Nano 3152 Auto Top Off ReviewTunze Osmolator Nano 3152 Auto Top Off Review
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Tunze Nano ATO Review

The Tunze nano automatic top off system is designed to increase the stability of your tank while reducing maintenance. This unit is made for up to 50 gallon tanks. I have had the Osmolator Nano 3152 on a 20 gallon nano tank for close to a year and a half now. So far it has done an excellent job for me.

Tunze Osmolator Nano 3152 Auto Top Off Review

Why do you need an automatic top off system?

An automatic top off system (ATO) is not necessary to be successful. However, you are much more likely to be successful with your tank if you have one. An ATO automatically adds fresh water to an aquarium to compensate for evaporation. This means the salt content in the tank stays stable, because salt does not evaporate with water. Stable salinity levels means happy fish and corals. You could add water to the tank yourself everyday to compensate for evaporation but this quickly becomes a hassle. The less maintenance you have to perform on an aquarium the more time you have to enjoy it.


There are 4 main components of an ATO system. Water level sensor, control module, water pump, and fresh water reservoir. The Tunze ATO system includes everything but the water reservoir. You can use any aquarium safe water container to drop the pump into that will be the reservoir.

Tunze Osmolator Nano 3152 Auto Top Off Review
Control Module – Water Level Sensor – Water Pump. -Click image to see on Amazon

Setup and operation is very simple. The water level sensor attaches to the tank with a magnet. Just place the sensor in the tank (or sump) at the water level you want to maintain. Plug the sensor wire into the control module. Drop the water pump into some sort of water container. Plug it’s wire into the control module and attach it’s water line to your tank (or sump) wherever you’d like. Tunze includes a nice little clip so you can easily attach the water line to the tank. Then just plug the control modules power cord into the wall and your all set. The setup is very straight forward and Tunze includes instructions.

Reliability and Safety

ATOs are a great piece of equipment but like anything they can fail and causes problems. If an ATO fails on (water pump keeps running) you could add too much freshwater to your tank or overflow it. This typically happens due to a water level sensor failure. This is why it’s important to buy a high quality product like this Tunze. The Tunze comes with an excellent water level sensor, however, just in case there is a safety. The control module will automatically shut down the system if the water pump runs for 5 minutes straight. This event would likely be caused by something like a snail pulling down the water level sensor. The sensor does have a built in guard to try to prevent this as well though.

In the year and a half I have run the Tunze nano auto top off I have never had a failure. I actually even add Kalkwasser to my freshwater reservoir which is very hard on the pump.


This is a high quality but affordable auto top off system. I would recommend this product to anyone with a nano saltwater aquarium. It is easy to set up and saves me from the hassle of having to add water to the tank myself everyday.

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