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Tunze Osmolator Nano 3152 Auto Top Off

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

Tunze Osmolator Nano 3152 Auto Top Off

90% Recommend this to a friend (44 of 49)

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".

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Previously Asked Questions

  • by Joe on February 25, 2014, @12:58 PM

    Other than the reservoir, What else is needed for this kit? Also, what is the maximum head height of the pump? Thanks !

    Bulk Reef Supply 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.

    Do you find this question helpful?  Yes   No

  • by Matt on December 16, 2013, @4:29 AM

    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?


    Bulk Reef Supply 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.

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  • by Clayton on August 29, 2013, @3:36 PM

    Why can't this model be used on a larger system?

    Bulk Reef Supply 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.

    Do you find this question helpful?  Yes   No

Full Details

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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  • 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.
  • GREAT SO FAR By MARK on 3/25/2015

  • Good for what I needed By Eric on 2/23/2015

    This is my first auto top off and it is working fine for what I have. The size is good and the pump is running great so far. I have only been using it about a week with only one small issue. That is, I can't find a way to have the pump sit level on the bottom of my reservoir. I think it will just take some time for the hoses and cables to stretch out. Overall, good buy for me though.
  • Dosn't fit rimmed tanks very well By Adam on 2/19/2015

    If you have a top rimmed tank this will still work but it will sit low in the tank, making the waterline below the rim. Contacting Tunze now to see what they are going to do about it if anything. Love their products but the mount for the float switch needs to go back to the drawing board. So as of now I either have to deal with the low water line or fabricate a custom mount. If the float switch fit better I would have given it a 5 star.
  • Nice auto top off By Todd on 2/8/2015

    Easy to set up and works great. My only complaint is that it needs a suction cup or something so that is attaches to the bucket as it just lays on its side without this
  • Good for a few months By Casey on 12/20/2014

    My second Ato has stopped working. When the unit works, it's great.
    When the first one stopped working, I reached out to BRS and Tunze. I learned that I was basically S.O.L without sending the unit back to them. I just decided to spend the money and buy a replacement.

    That was a workable plan for a few months until the second unit died on me. I've decided not to buy another. I'd rather pour the RO water in myself than purchase yet another unreliable model from BRS. I hope they find a more reliable nano ATO to promote.
  • Works well fills need By Thomas on 12/9/2014

    Bought this to top off my nano tank. Set up was easy and does a good job maintaining water level. Lot less hastle than topping of tank daily and keeps salinity more stable
  • Can't imagine how I lived without this thing By Sean on 12/4/2014

    No more lugging around jugs every other day, now it's only once every couple weeks! :) This is a huge upgrade and peace of mind. I have a small tank so this is huge in helping me keep my water parameters stabilized. This is a must-have for smaller reef tanks for people serious about their corals.
  • Works great By Meaton on 11/19/2014

    Perfect for my nano cube 28G reef tank
  • Compact. Works well. By Joseph on 10/29/2014

    The unit is very compact, works well, and maintains your water level with frequent small top offs.

    My only complaint is the pump doesn't have a suction or bracket so that it sticks to the bottom/side of your reservoir bucket.
  • Replaced Hydro-fill By peter on 10/7/2014

    I owned the IM Hydro-fill for about 6 months when the controller went out. I've only had the Tunze running for a couple of weeks but I like it better already. Triggers from slight water level drops and I like the idea of the built-in fail safe.
    Only complaint is the pump is pretty loud.
  • 14days Dead By Richard on 9/12/2014

    problem for the controller pump not working

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