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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 (223 of 229)

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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Previously Asked Questions

  • by Spencer on April 29, 2014, @12:54 PM

    I have a litermeter 3 that has failed. It pushes water about 30 feet from the litermeter to a sump tank. Will this pump do the same?

    Bulk Reef Supply Hi Spencer,
    The max head pressure on the included pump is about 7ft. It likely wouldn't be well suited to this application. That said though, you can get the additional switch socket adapter which would allow you to control any pump via the osmolator system. That way you can use a pump that can handle the head pressure.

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  • by Jeff on November 28, 2013, @2:50 PM

    How much head will the pump push

    Bulk Reef Supply Hey Jeff,
    The pump on the osmolator has a max head height of 7ft.

    Do you find this question helpful?  Yes   No

  • by Christian on July 17, 2014, @9:40 PM

    If i have a wave maker and this ATO in the same tank (I don't have a sump), would the waves cause the pump to turn on and off constantly? Thanks

    Bulk Reef Supply Hi Christian,
    In theory it could present a problem but the circuitry in the Osmolator should help to prevent that. Every time the ATO is triggered it runs for a minimum of 15 seconds. It adds overfill to prevent short cycling. In most cases this should be sufficient unless the height of your waves is constantly changing.

    Do you find this question helpful?  Yes   No

  • by David on May 10, 2014, @11:50 PM

    Would you happen to know the max head pressure of the Tunze Osmolator's pump?

    Bulk Reef Supply Hi David,
    The max head pressure on the osmolator pump is 7ft.

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  • by BILL on November 13, 2013, @7:37 AM

    what pump do you suggest to go with the3155 osmolator?

    Bulk Reef Supply Hey Bill,
    The Osmolator actually comes with the pump right in the package so you don't need to buy one!

    Do you find this question helpful?  Yes   No

  • by Ronald on January 13, 2014, @2:32 AM

    Just wondering if I need 2 ATO. I know you can place it either in the sump or in the tank, but my question is if I place it in the sump will it also refill my tank in that process. I don't see that happening but if it does please let me know.

    Bulk Reef Supply Hi Ronald,
    If you have a sump, it MUST go in the sump, in the chamber where your return pump is. This is the only area of your tank that will have a changing water level depending on evaporation (unless its far too late!). Only one ATO would be necessary but it must go in that location if you have a sump.

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  • by Daire Fontaine on January 17, 2014, @12:23 AM

    My Tunze Osmolator ATO keeps getting stuck in the ON position. I soaked the electronic eye in vinegar and it was fine for a week, but then it stuck on again. Do these electronic eyes fail after many years of use? I've been using it for about 4 years. Is there any way to replace the eye without having to buy a whole new system?

    Daire Fontaine

    Bulk Reef Supply Hi Daire,
    We run into very few issues with these but after that length of time I would imagine its possible for any component to fail. We don't have individual parts like the optical eye, but if you give Roger and company a shout over at Tunze USA, he might. At the very least he could likely help you narrow down exactly what it is. The number I have for them is 512-833-7546 tunze@sbcglobal.net

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  • by Mark on June 5, 2014, @8:39 AM

    Does the pump get placed directly in the top off water reservoir? If so what are the dimensions of that pump? I am trying to decide what kind of reservoir I can use before purchasing a ATO.

    Bulk Reef Supply Hey Mark,
    That is correct. Its a submersible pump that gets stuck right into the top off water. If your interested in this ATO system you should give this blog article a quick read. It goes into a lot more detail on the system (which is one of my favorites).


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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.



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  • Would recommend this product to a friend By James on 4/12/2015

    I liked this ATO so well I bought a second one for a tank I have set up in another part of the house. Its simple to use and maintain. The instructions are almost too detailed, in my opinion, I had to read them several times but they are effective. I like the two different means of shut off, the electronic sensor and the float valve. BRS TV should consider a video installing one of these and setting up the electronic eye, to support the complicated instructions. Great product IME.
  • Best ato By Mike on 3/29/2015

    I pick this unit up two years ago on Black Friday and it's been running like a champ since. as the BRS YouTube video indicates the laser as well as the mechanical part of this provides a great backup is fairly easy to put together which sometimes is in the case with Tunze Products but this is been doing the job for two years.
  • Works perfectly By Chris on 3/27/2015

    I love this thing. It works perfectly and has never failed. Not much else to say than that.
  • eliminated manual topoff By Greg on 3/23/2015

    I like it So far no issues. The reviews were good. Instead or trying something I am usually using others experiences to save me the anguish of poor decisions
  • A necessity By JonnyReefer on 3/19/2015

    It's so nice not having to get 3 half-gallon cups per day and bend down to refill my sump. And no more micro-bubbles! Although the little nut&bolt that holds the output line to the tank attachment was a PITA to get on, it was a breeze to set up.
  • ato By luis figueroa on 3/19/2015

    bought my first ato about two weeks ago and I must say its been the best purchase ive ever made in this hobby. keeps water level and stability in parameters. so far so good.
  • tunze 3155 By Derek on 3/18/2015

    I love this thing. no more worries when im not around for a few days. works excellent just as expected from tunze. easy to set up
  • Easy to use and no need to worry about your tank By Hamad on 2/28/2015

    It saved my time and i do not need to manualy add water. i used it for 200 gallon tank. Thanks BRS
  • Super Product By RDM on 2/20/2015

    This was easy to setup and get working. I never realized how much I hated having to manually top off my water until I put this in my system. Now I just check my water levels and the fresh water supply and this takes care of adding water as and when it's needed.
  • EASY and works great By Jeffrey on 2/15/2015

    So far so good ! Have this set up on roughneck bin I'm using to cure my dry rock in. Works perfect and secondary safety offers great piece of mind. In the room one day when pump came on.. manually lifted float and audible alarm sounded and pump shut off. Very comforting to have a piece of equipment like this that is looking out for me ! If you are on the fence, JUST GET IT, you won't be disappointed.
  • fantastic ATO By Hawrasser on 2/11/2015

    this ATO is great. keeps the water level in my sump constant. the only thing i would change is to make the amount of travel on the floating switch a little bit larger. if i turn on my protein skimmer it will sound the alarm but my skimmer is also huge haha
  • 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.

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