Osmolator Nano 3152 Auto Top Off - Tunze

Tunze Osmolator Nano 3152 ATO
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  • Tunze Osmolator Nano 3152 ATO
  • Tunze Osmolator Nano 3152 ATO Floats
  • Tunze Osmolator Nano 3152 ATO Pump
  • Tunze Osmolator Nano 3152 ATO Included Parts
  • Tunze Osmolator Nano 3152 ATO Magnets
  • Tunze Osmolator Nano 3152 ATO Power Supply
  • Tunze Osmolator Nano 3152 ATO Box

Osmolator Nano 3152 Auto Top Off - Tunze

90% Recommend this to a friend (54 of 60)

SKU: 202331

reg. $106.99

Special Price: $99.37

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Quick Overview

The Tunze Osmolator Nano 3152 Auto Top Off is designed for smaller tanks, approximately 50 gallons and under. One of the safest ATO’s available. Utilizes an single sensor to monitor water levels and a controller that protects against overdosing. Magnetic holder for sensors up to 10mm or .39".

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Product Questions

Hey brs,
What's the main differences between the nano and the 3155? Also, would be possible to upgrade in the future without having to buy the whole thing?

Question by: Matt on Dec 16, 2013 4:29:00 AM
Hi Matt,
The nano osmolator is just a simple float switch and that is it. The 3155 has the dual level control with the optical eye for primary control and the float switch emergency backup. The 3155 offers superior redundancy.

It would not be possible to upgrade, they are entirely different units.
Answer by: Bulk Reef Supply on Dec 16, 2013 4:29:00 AM
Other than the reservoir, What else is needed for this kit? Also, what is the maximum head height of the pump? Thanks !
Question by: Joe on Feb 25, 2014 12:58:00 PM
Hi Joe,
Other then the container the kit really comes with everything you need to get started. The pump has a max head height of about 7ft.
Answer by: Bulk Reef Supply on Feb 25, 2014 12:58:00 PM
How much travel between on and off with this sensor? 1/3"/ 1/2" etc.?
Question by: Scott butcher on Jan 18, 2016 10:13:00 PM
Great question!
The distance between the float being triggered and off is between 1/4" to 1/3" Feel free to let us know if you have any further questions!
Answer by: Connor (Admin) on Jan 27, 2016 2:17:00 PM
I recently purchased one of these and think I will LOVE it but have a question. Each time I have gone to check on it, it seems the relay/sensor (whatever we call it) has shifted slightly so it is no longer sitting level. This is help on with the magnets, so am curious as to why this is happening or what I can do to stop it!
Question by: Wendy on May 18, 2015 12:54:00 PM
Great Question,
You can always try implementing a large magnet to ensure the hold is stronger. Other than that, there are some more permanent applications such as small amount of super glue. In any case your best bet will be to contact TUNZE and see if they have any tips or tricks.

Tunze – 512-833-7546 tunze@sbcglobal.net
Answer by: Connor (Admin) on May 18, 2015 7:15:00 PM
Does this model have an optical sensor such as the one in the larger model?
Question by: Tristan B on May 4, 2016 2:47:00 AM
The Nano will not come with an optical eye. Only the standard float switch. Feel free to let us know if you have any further questions!
Answer by: Connor (Admin) on May 4, 2016 2:01:00 PM
Why can't this model be used on a larger system?
Question by: Clayton on Aug 29, 2013 3:36:00 PM
Hi Clayton,
The unit is not suited to large aquariums because it has a timer based cut off so the pump will only run for a short period of time. Using it with a large tank can result in the the pump turning off before its finished replacing the evaporation.
Answer by: Bulk Reef Supply on Aug 29, 2013 3:36:00 PM

Full Details

Owners Manual



Introducing the little brother to the Tunze Osmolator, one of the industry’s most trusted automatic water top-off device and BRS Recommended. Designed specifically for smaller aquariums, roughly 50 gallons and under, the Osmolator Nano 3152 is a slimmed down version of the full sized 3155. It includes a processor-based anti-overfill system which turns the pump off if after five minutes of filling the level has still not been reached. The Osmolator Nano includes the control unit, low voltage (6V) pump, power adapter, 3m hose, magnet mount and protective cover.


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  • Had defective pump By Mike on 4/25/2016

    My experience is mix. The product works well for 10 days then stopped. Tunze customer service replace the pump and is wrking fine now. Just the trouble of not wrking and having to contact Tunze for replace part.
  • Works great! By Rachelle on 2/15/2016

    This is a very nice ATO system, it works like a charm and keeps my salinity nice and stable. My only complaint is that it doesn't have a way to keep the pump sitting flat.
  • Amazing By Jack on 1/14/2016

    i have been looking for an ato for a while, and i found tunze's products. i didnt really want to spennd $200 on the osmolator, so i tried the nano osmolator. works great, and has an auto shut off just in case it fails. another quality product by tunze
  • Terrible By Brandon on 8/31/2015

    The reason why the normal tunze osmolator does so well and sells so often is because the eye sensor it has well in this Nano version there's none witch makes this just as good as a lowest model auto top off u can buy for a few dollers or even make not worth it and don't use it trust me
  • Great Nano ATO By Sterling on 7/23/2015

    This is an excellent ATO. I'm new to reefing and everywhere I read ATO's were on top of the suggestion list. I bought this with everything else to setup my new tank and I'm very glad I did. It was easy to setup, works as advertised, and leaves a little footprint. Worth the price and it's one less thing I need to worry about.
  • Love this thing By AdamNC on 6/29/2015

    Been using it for a few months now with little issues. One issue is with the supplied hose the pump in the reservoir tends to sit sideways. But that's not fault of the actual equipment just the hose. And on a rimmed tank it does make the water line sit about 2-3mm below the rim. Nothing major just a peeve but I'm used to it now. It actually allows me to see that the water line is constant in the tank. Other then those two things I love it. Mechanically I've had no issues.
  • Should have got this a long time ago. By DadE on 6/26/2015

    Works great and on my way to a stable reef.
  • excellent By Redick on 6/23/2015

    I placed this on a 60 gal. It does exactly what it advertised very very well. An excellent product. East set up and easy to use.
  • Very good product and easy to setup By Joe on 6/18/2015

    very good product, easy to setup and it works very well
  • Even a caveman can do it! By Ed on 6/1/2015

    Easy setup, Works like clockwork! no more salinity variability, Woohoo! I use a 2.5 Gal reservoir and I have plenty of water for 1 week of top-off!
  • Painless set up works great!! By Amin on 4/27/2015

    This ato work as advertised. Its easy to set up and helps keep my parameters in check!!
  • Convenient By Mark on 3/26/2015

    I added this to a rimmed 29 gallon tank. In order to keep the water level above the outside trim I had to cut part of the inner rim off to raise the magnet and float switch. This wasn't necessarily an issue because I knew I was going to have to do that before I bought it. Just something to be aware of. I find that it will turn on and replace almost exactly the amount of water I had been adding manually each evening so that's nice. Since it's on the main display it doesn't turn on very frequently. The pump is audible but not terribly loud and it doesn't stay on for long. I actually like that I can hear it. I know it's working! An issue I have been having is due to the setup of my tank I had to place it near the hob skimmer and bubbles from the outlet on the skimmer have a tendency to get trapped under the float and make it not operate correctly. It's not a huge problem and could be avoided by placing the float farther away from something that produces bubbles. I also have a wavemaker that can make the pump turn on and off from the waves it produces. Again that can be addressed by creating less waves or putting the wavemaker and/or ato on a timer. I'd recommend this because it works pretty good and has a fairly small footprint if you want to keep it in a display tank. If you have a sump the issues I've had probably wouldn't exist. There might be some better ones out there but it suits me for now.

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