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

83% Recommend this to a friend (58 of 70)

SKU: 202331
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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".

Max Head Height: 7.0 ft


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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
what if you dont have a sump, can you put the controllers directly in the aquarium?
Question by: val sammut on Jan 12, 2017 12:15:00 PM
Great question! Yes you can mount the sensors directly in the aquarium. However you may have an issue with keeping the sensor stable if there is a lot of surface agitation in the tank. :-)
Answer by: Randy (Admin) on Jan 12, 2017 2:18:00 PM
Can you increase/decrease the pump flow like the 3155?
Question by: Eric Finney on Dec 4, 2016 8:18:00 PM
Great question! You cannot make any adjustments to the Nano Osmolator. :-)
Answer by: Randy (Admin) on Dec 17, 2016 7:57:00 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
Hey guys, I've been thinking of adding an ATO to my 120gal reef. The price difference in the 3155 and 3152 is a factor. Does the 3152 nano also have a 10 minute internal shutoff timer? Or the ability to adjust the flow rate of the DC pump?
Thanks for the feedback.
Question by: Brad on Jun 7, 2016 12:08:00 PM
Great question!
the Nano will have a 5 minute shut off and no ability to adjust he flow of the pump. In most cases this will be too limited for the 120 gallon. Feel free to let us know if you have any further questions!
Answer by: Connor (Admin) on Jun 7, 2016 6:02:00 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
If this pump were to break could you use the Apex Neptune PMUP as a replacement for this system?
Question by: Sean on Dec 21, 2016 1:24:00 AM
Great question! This pump cannot be used with the Tunze ATO system. The Tunze utility pump is proprietary to their ATO controller and must be replaced with their brand pump. :-)
Answer by: Randy (Admin) on Dec 21, 2016 4:17:00 PM
I was curious if this auto top off will work for my Innovative Marine NUVO 10. Would the water get too salty by the time the ATO kicks on?
Question by: Trenton on Jul 7, 2016 12:21:00 PM
Hi Trenton,
That is a valid concern and if you are keeping SPS in the 10 gallon then we would suggest looking into the Osmolator 3155, however for most fish, and other corals like softies and LPS the Osmolator nano will work just fine. Since the return pump compartment is much smaller than larger tanks, when water evaporates it will move the water level pretty quickly and activate the float switch which is pretty sensitive.
Answer by: Charlie (Admin) on Jul 7, 2016 12:42:00 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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  • Good for the price By Doug e fresh on 4/10/2017

    I have only used this for a month and it has worked well. The only problem I have is I don't quit trust the single float switch.
    But time will tell if I learn to trust it.
  • Not typical Tunze quality By Mark on 2/27/2017

    Bought this thinking I would be getting the same quality as it's big brother, but this one is complete garbage. The pump has failed on me several times, requiring me to unplug it and plug it back in. Luckily I caught it quickly each time, but I definitely wouldn't trust this if I went on vacation. Also, unlike it's big brother, this ATO only has one sensor (a float sensor) that is prone to getting stuck. I would recommend only getting the bigger osmolator or using a different brand that uses an optical sensor.
  • Pump Issues By Matthew on 2/23/2017

    There appears to be issues with pump quality of these units. The pump that shipped with my nano could only develop about 2 inches of head.

    Tunze sent me a second pump which seems to be ok.

    NOTE TO CANADIAN CUSTOMERS: You may have issues with warranty processing in Canada. Tunze Canada will not honor warranty on products purchased in the US, Tunze USA will only cover the parts and labor on products in Canada due to expensive shipping costs to Canada.
  • Would not recommend By Wilson on 12/12/2016

    I bought this with the idea it would make my life easier. The first pump failed and Tunze replaced it. The second pump ran great for @ a week then stopped filling up the tank unless I unplugged it and plugged it back in. They are now sending a third pump however I'm not holding my breath. Had I known this would happen I would have purchased another model.
  • Excellent product By Richie D on 11/4/2016

    Sure is convenient not having to add to-off water all the time. Just went away for the weekend and didn't have to worry about whether or not the gravity fed system I had always used would work or not. Many times I would come home to find the pump sucking air and the aquarium down about 4 inches. Not this time! While it is very expensive, it does save a lot of headaches and potential loss of fish and corals. Absolutely recommend it.
  • Great mini version of the bigger ato By Sgt Harold on 9/13/2016

    I brought this for my Red Sea max 250 rimless . It has a small tank that I use a 5 gal bucket to keep full. Keeping salinity if important in maintaining a stably ecosystem .
  • Part #4017.000 Controller Osmolator nano device By Max on 8/3/2016

    I have written to the company in Germany to try to get a new part #4017.000 Controller Osmolator Nano device. I have to unplug the device and reconnect it every cpl days to get the unit to work properly to top off. It makes a noise like it wants to pump water to my reef tank but will not until I unplug the device and re-connect it then it works for a day or two. I hope I can get a replacement part as I only bought this from BRS beginning of July last month. I sent the scan of my invoice to the company in Germany as well so waiting on a response.
  • Great By darryl hey on 8/1/2016

    have 3 of these on nano tanks 29 biocube 40 breader and 45 cube works great! have been running for 2 years now
  • Auto shut off By Chris on 7/2/2016

    The float sensor got stuck on and the pump did not turn off. The auto turn off did not work. Luckily the story revisor was almost empty and my tank did not overflow. I don't trust it any more need to upgrade to the one with the optical sensor.
  • Great nano ATO By Tommy on 6/13/2016

    I installed the Tunze nano ATO in my Corallife Biocube 29. I placed it in the 3rd chamber with the return pump. So far it works perfectly. It has helped stabilize the tank and my corals could not be happier. Great little ATO.
  • 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.