Tunze Osmolator Universal 3155 Auto Top Off

Tunze Osmolator Universal 3155 Auto Top Off
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  • Tunze Osmolator Universal 3155 Auto Top Off
  • Tunze Osmolator 3155

Tunze Osmolator Universal 3155 Auto Top Off

97% Recommend this to a friend (212 of 218)

SKU: 202307
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Quick Overview

One of the safest ATO’s available. Utilizes an electronic eye sensor to monitor water levels and a backup float switch sensor with audible alarm. A controller protects the quiet metering pump from running dry and reports an empty storage tank. Two magnetic holders for sensors and multiple mounting brackets included.

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Full Details

Bulk Reef Supply tried many different water level switches and auto top off solutions before giving the Tunze 3155 Osmolater Universal Auto Top Off BRS Recommended status. Despite its higher price this is by far our favorite solution. Spending the extra money on a Tunze Osmolater will give you that extra peace of mind and insurance from having a disaster that ruins carpets or hard wood floors.



  • Hoping to get it working By Andrew on 1/16/2015

    I have had this on an AIO tank (40 gallon) worked great the first week, now it keeps overfilling my tank( alarm going off) in the process of troubleshooting it with Tunze, hope i can get it to work correctly. I wish it worked right out of the box, but based on reviews the Tunze auto top off is suppose to be the best. I have owned other Tunze products before with no problems. Not bashing the auto top off but its not working out of the box. But Tunze customer service is great at helping.
  • Great ATO! Never missed the target! By Alec on 1/15/2015

    I don't need to add anymore to those 200+ reviews but I put mine on a timer that only turned on once a day for 10 mins. That way it's not pumping all day long and will never over fill.
  • Works Great By John B on 1/10/2015

    Easy set up and I love the optical sensor. My old ATO float valve would often not register the water level depleting and I'd have to refill the sump manually. No issues so far and don't anticipate any. I did have to run the top off line into the tank overflow since my storage container is taller than the sump, but there was plenty of supply hose and I actually like it better.
  • Best ATO ever By Seadog09 on 1/7/2015

    The name alone represent quality so you know from start to finish that's what you'll get. I'm happy with my purchase and I know you will be too..
  • Works flawlessly. By DivingTheWorld on 1/5/2015

    I've had this running for about 4 months now and it works flawlessly. It's really a set it and forget it product. The one quirky thing is that when it first turns on, it will pump water for a few seconds to purge the pump of any air. This is normal and not a but per say, but something to be aware of. I initially had this programmed on my Apex to only turn on a few times a day, but found that it was pumping too much water (due to the starting purge). So now I just leave it on 24 hours a day and it works fine.
  • Works as promised By Jay B. on 1/4/2015

    I bought this to regulate the level in my sump, using RO/DI feed. I also purchased the optional valve. The setup is easy, especially because of the way that the two level sensors are cleverly mounted with the magnetic holder. I turned the water feed on on and everything worked like it was supposed to. Now I don't have to keep fiddling with my protein skimmer to get the right quantity skimmate.

  • Almost perfect By Jim on 12/27/2014

    This is a really great ATO system. There is one downside. If you are pumping the water into your sump, the top level of the top off water container supply cannot be higher than the sump water level. The pump is centrifical, and allows water to flow through the pump when it is off. If the top off water is higher than the sump water, a siphon will occur, and water will continue to flow until the water levels equalize (including over-running the sump, and onto the floor. You simply need to select the right top off container.
  • ATO's Don't Get Better Than This! By Bernie on 12/20/2014

    The Tunze was superior to my first ATO set up which used a float valve and lifter pump. The optical sensor is great and having the second float valve to protect against overfilling is just a smart investment to protect not only your tank but the flooring around it.

    I have a controller in which I could probably have set something up myself but for an all in one package this system is great.
  • Very Cool! By Trent on 12/16/2014

    This is a great product. Easy to setup and trouble free.

    One funny thing is that the way that the LED indicator lights are mounted inside the control box allows for "bleed over" from one light to another. So, in my particular case, the way that I have it mounted inside my cabinet makes the "Too High" appear to be lit when in fact it's the "Level" light. It took me a couple of plug-unplug cycles to figure that out.

    But, it's great product. Recommended!
  • Still the best! By Martin on 12/15/2014

    There have been a lot of additions to the ATO market over the last year or so. The Tunze 3155 Osmolator is stil the best unit on the market. Reliable and dependable. If you're undecided because of price, don't be...just buy it and be glad you did.
  • Works flawlessly By GARY on 12/15/2014

    Bought one thanks to the positive reviews here and I owe the reviewers here a debt for getting it right and saving Me Money making a mistake.

    Want an ATO, click 'ADD TO CART' on this and be done with it.
    Works flawlessly
  • great product By kalen on 12/11/2014

    I recently bought the tunze ato and I had heard many good things about it. I did many months of research and I finally decided to buy it and replace my smart ato which was always failing. I would recommend this product to others

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