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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 (234 of 242)

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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Product Questions

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?
Question by: Spencer on Apr 29, 2014 12:54:00 PM
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.
Answer by: Bulk Reef Supply on Apr 29, 2014 12:54:00 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
Question by: Christian on Jul 17, 2014 9:40:00 PM
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.
Answer by: Bulk Reef Supply on Jul 17, 2014 9:40:00 PM
How much head will the pump push
Question by: Jeff on Nov 28, 2013 2:50:00 PM
Hey Jeff,
The pump on the osmolator has a max head height of 7ft.
Answer by: Bulk Reef Supply on Nov 28, 2013 2:50:00 PM
Will this work with the Apex controller?
Question by: Jim on Aug 3, 2014 11:31:00 AM
Hi Jim,
The Tunze Osmolator is an entirely self sufficient system. It is perfectly fine to connect the Osmolator to one of the Apex's power outlets incase you wanted to cut the power for some reason (like when you are doing a water change) though the Apex isn't capable of reading the Osmolator's sensors or anything of that sort.
Answer by: Bulk Reef Supply on Aug 3, 2014 11:31:00 AM
Would you happen to know the max head pressure of the Tunze Osmolator's pump?
Question by: David on May 10, 2014 11:50:00 PM
Hi David,
The max head pressure on the osmolator pump is 7ft.
Answer by: Bulk Reef Supply on May 10, 2014 11:50:00 PM
what pump do you suggest to go with the3155 osmolator?
Question by: BILL on Nov 13, 2013 7:37:00 AM
Hey Bill,
The Osmolator actually comes with the pump right in the package so you don't need to buy one!
Answer by: Bulk Reef Supply on Nov 13, 2013 7:37:00 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.
Question by: Ronald on Jan 13, 2014 2:32:00 AM
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.
Answer by: Bulk Reef Supply on Jan 13, 2014 2:32:00 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
Question by: Daire Fontaine on Jan 17, 2014 12:23:00 AM
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
Answer by: Bulk Reef Supply on Jan 17, 2014 12:23:00 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.
Question by: Mark on Jun 5, 2014 8:39:00 AM
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).


Answer by: Bulk Reef Supply on Jun 5, 2014 8:39:00 AM

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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  • great customer service By dozer42 on 6/20/2015

    My ato quit working. Contacted tunze and they had me send it in. Long story short my pump went bad and burned out the controller unit. I had to buy a new pump but even though my controller unit was out of warranty they replaced it for free.
  • Must Have By RICHARD on 6/16/2015

    This works great and the two different sensors are awesome. I even plumbed this to feed my two foot tall DIY kalk reactor and it feeds the reactor with no issues.
  • Get it. By Michael on 6/12/2015

    This is my first and probably the will be the last ATO system I will need to buy...unless I set up another reef tank of course. Forget about the "hefty" price tag, your tank is certainly worth it.
  • Excellent product! By Joseph on 6/1/2015

    I have this setup currently for my system. While the instructions are not as straightforward as I'd like, there are plenty of videos online to learn how to set everything up. There are several ways to use this product which are part of what makes it good but also part of why the instructions are a little confusing. Nevertheless, it works great and worth the money IMO. Get it.

  • Fantastic By Plomanto on 5/28/2015

    This thing is awesome . Very easy to install and works exactly as described. I highly recommend this product for any one looking for an ATO
  • over 5 years and it is the best! By mathdoc on 5/22/2015

    I have had one of these as my overflow system along with a 20 gallon food grade trash can filled with water plus some Kalk for over 5 years. When I first purchased it, I remember reading it might not last with kalkwasser. Well, 5 years and 1000s of gallons later, the unit is still functioning perfectly. When it dies someday, I will not think twice about purchasing any other brand. Don't think twice, this is the best top of on the market!
  • Mixed feelings By Wolfentank on 5/16/2015

    I've been using one of these for about 8 months or so, and I can't say that I love it or hate it. It's possible that my unit may have a defect as it will occasionally over fill and trigger the emergency alarm. At the same time I had a cheap $10 float switch/dosing pump set up on a nano tank that was flawless. Overall, this is a pretty good ATO and I do like the alarms. I wish it had some kind of switch to turn it off/on for when I'm doing water changes though.
  • Worth every dime! By Gerry on 5/14/2015

    The $200 dollar price tag is a little hard to swallow... But the peace of mind is completely worth it. Even though the instructions were a little hard to decipher because their English was badly translated(at least for me it was) the set up was simple and quick.
    I did have a defect with the laser eye but BRS was super quick on getting squared away.
  • Wish everything was this easy. By jon on 4/27/2015

    drop it in tank. connect a few wires. fill container. set optical level. done...
    only issue i had i had to call to figure out where the sensor picked up its not the tip its the beginning of the cone. has multiple sensor options and fail safes. highly recommend.
  • would recommend this product to a friend and reefer By Frank on 4/27/2015

    This is my 2nd one have two tanks 90 gallon and 180 gallon on my 180 Gallon have been running the 1st one for over two years now and have not one issue the best thing out there, I have used, different ATO but this is the one everyone should go with. ALL REEFERS THIS MUST HAVE save you lot of time. Just set it up keep water in the pump unit that you used and walk away.
  • Perfect..!! By Dinoflagellates on 4/23/2015

    I should bought this ATO a year ago an forget the daily top of. This set is all I needed for my 150 gal reef aquarium..!

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