Comments: I've been through a couple ATO's over the years and it's time to switch to a different brand. When this arrived and was unboxed I notice the quality in it right away. The way the manufacturer took the time to bubble wrap blahh blahh.. Everything is included (literally everything), easy to set up & seems to be fail proof unlike JB

Comments: After debating and searching for a couple of months I decided to spring the extra cash for the Osmolator. It had come down to this or the SpectraPure UPLC. I am a very picky consumer. My main concern was using it in a display tank and being able to set it to keep the water level as high as I wanted. It does keep it a little lower (I was keeping it right to the lip (widway point of the top trim) about 1/2" from the very top of the tank. With the sensor at the highest setting (mounted in the display right below the lip on the trim) it keeps the water level exactly at the bottom line of the trim on my 40 breeder it worked out to where I had to remove apx 1gallon from the previous level I kept it at. But at least it is not visible from looking at the tank straight on. Setup was a breeze. I did NOT have any problems with the sensor, bubbles, or breaking it in, etc. Right out of the box it functioned flawlessly. Now instead of lifting and manually dumping 1/2 gallon of RODI twice a day I just fill my custom 7gallon reservoir once a week during the water change and I don't have to worry about it. I work random hours and travel a lot, having someone reliably keep the tank topped off was my biggest worry and now that is eliminated. The slightly lower water level is a non issue, you can't see the line and the peace of mind of knowing my salinity is staying more steady is well worth the trade off. Highly recommend this product!

Comments: Every reefer should have one.

Comments: Unit seems to function very well. Instructions nearly impossible to understand. Customer support excellent.

Comments: best one out there, very nice setup.

Comments: easy and simple.

Comments: seems to keep sump at pretty consistent level, a little more complicated than JBJ, but I've had the JBJ overflow my sump several times now, when the sensor failed to turn off the pump. The Tunze has a built in safety sensor to prevent this, and seems to keep water level more consistent with 25 mm variation.

Comments: Excellent product... 15 minutes from box to topping off tank... Now I only have to top off the top off reservoir with 8 gallons of water every 5 days or so... Maintains water level within 1/8"... Very finished look... Two thumbs up!!!

Comments: The Tunze 3155 is in my experience the best ATO for the money hands down. Simple to set up with options for you to be able to customize your water leveling needs. I like that the unit comes with two sets of magnetic placements so if you want to have your emergency shut off in a different location then the inferred eye you can. I also like the pump chosen to go with the unit. Being that it is a bottom feed sump pump the water in your reservoir is almost always all used giving you more time before having to refill the backup water. Having a monitor that will show you when it

Comments: Do not think just buy it, you will not regret.

Comments: I have it on Red Sea Max 250. It took about a half an hour to install. Used the mounting magnet and it was easy. Good product plug and play.

Comments: Very easy to install, glanced at instructions and everything was very straight forward. Had to add a gallon a day now dont have to worry about rushing home to check on tank. Love it

Comments: The Tunze Osmolator does it's job well. Very stable salinity with almost no fluctuation in my sump, something to be carefull with though is the presence of micro bubbles in the sump, if they collect on the eye (sensor), the controller will get a faulty reading and the pump will run until the h20 level reaches the saftey switch level. So if you have to fine tune your sump by adding another baffle, or a bubble trap, and or dial back you return pump you should do that first. Then buy this auto topoff! It's quite and has a reputation of dependability.

Comments: The installation and setting up the senors to the dept that i needed was easy. This gave me more breathing room,knowing that my system will be running without having the sudden drop and raise of salinity level in the tank. It is a very competitive price compared to other sellers....Totally recommend to anybody who wishes to do salt water fish or reefing for a long time..

Comments: just recived and installed tunze osmolator 3155 on 60 gallon reef tank.installed in sump. easy to install and setup. holds water level in sump to within one half inch.i think this topoff is going to make my life much more simple. only been installed one day now. will have to see long term.

Comments: This works great and I wish I had bought this a year ago. As several have mentioned, make sure there are no air bubbles around the sensor and let it "break in" my immersing for a few hours before the first test (mine didn't read the first level at the first go, but next day it worked and has worked flawlessly after that.I only gave it four stars because the retailer doesn't carry the switched outlet, which I had to get elsewhere. That allows me to run another pump and have my water source in a 40 gallon drum in another room.THe directions could also be better, but it is fairly easy to figure out.

Comments: My Tunze died yesterday, even with the sensor out of the water, the controller failed to start pump. Tunze carries a two year warranty. I was told to send it back for repair or replacement. I will update this after 6 months to report back.

Comments: Have not encounter any problem yet,this thing works great.It should come with the bracket though considering the prize.

Comments: Been up and running for about a month with zero problems. Easy to set up and I can't believe I waited so long to buy this! I went away for a week over New Years and I didn't need anyone to come over and fill up my tank.

Comments: Perfect -- all you need in one complete package! Easy to install and setup.

Comments: Bought this as a replacement to a peristaltic top-off that quit working. This unit works better in every respect. There are 2 sensors - a solid-state low level sensor and a movable high level sensor to prevent overflow. Therefore a snail crawling on the low level sensor will not cause the pump to keep going and overflow the aquarium. The pump moves good volume and sits firmly on the bottom of my reservoir. The other unit kept lying sideways and would suck up air when the water level got low. Much better pump and as I have learned you get what you pay for.

Comments: This is a very nice unit and it performs well. When I read initial reviews, I was concerned about the pump life expectancy. Many people had to replace the pumps after a year or so. I use this in a reef tank with buffered RO/DI water and the pump has lasted for over three years. The entire unit has performed without issue since May of 2008. Yesterday, 11-1-2011 the controller failed and ran the sump low on water. The controller is in a closet away from the main tank. I'm disappointed in the controller, but happy with the performance in my application. I don't see just the controller offered for sale either.

Comments: Just installed it this past weekend - works great, time saver, won't have to worry as much on salinity and with my Kalkwasser unit, it makes everything much more efficiently! Highly recommend.

Comments: Great product! Easy to use. Pretty easy to set up. Instructions come in 6 different languages and two separate books, and it comes with more parts than anyone really needs. Overall, I couldn't have asked for more!

Comments: This unit is amazing. It was a little tricky trying to adjust, but that was not the fault of this device, it works great. My problem was my protein skimmer putting too many bubbles into my sump that kept affecting the electric eye. But thanks to the second float level I never overflowed my tank or sump. Fixed the bubble problem and everything is working great and it is very quiet and runs smoothly. I did silence the alarm because a timer for feeding mode which cuts off my pumps and skimmer that causes the water level to go higher than what I have set up for the top off unit and I didn't want to hear the alarm every time it was time to feed the fish and coral. I am glad I made the investment for the Tunze Osomolator and expect nothing but the best from the unit. It was easy to install and had no problems with the directions. The electronic eye is very sensitive and precise. Yeah, no more having to carry the 5 gallon jug everyday. Just once a week to fill the storage bucket. I would highly suggest this to others. Just bite the bullet on the price and get this if you want a worry free solution to having to add water everyday.

Comments: Like many others that reviewed this product, the instructions were tough to understand so unlike the pre-Internet days:-) I did a quick search on YouTube to get the basics down. Once it was set up it was easy to see the fine German engineering. I've owned German cars and the product design of this was as well thought out as an Audi.
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<br />This is being used in the Oceanic Biocube 29, the sensors & top off hose located in the third chamber with the return pump.
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Comments: I have 3 of these, 2 on tanks at home, 1 on a tank in my office. They are the perfect solution, well worth the money. As long as the reservoir has water, they work exactly as they should. The pump can be a little loud, but if the reservoir is hidden in a piece of furniture, you likely won't be bothered by the noise. A quick swipe with a clean cloth of the optical sensor once a week, and you're done with maintenance. It's so efficient, that I have to remember to unplug it while performing a water change! No more lugging gallons of water around daily - now I can fill the reservoir once a week and forget it!

Comments: After a 'break-in' period of a couple of days (I'm assuming the optical sensor needs to build up some sort of film) it began working as promised.
<br />The documentation is probably great if you understand German. If not, the pictures will walk you through the set-up and operation.
<br />After reading other reviews, the first thing I did was to disable the audible alarm (easy enough with a jumper switch). The "Water too high" alert will trip when the float switch is activated.
<br />So far the unit seems to be operating as expected.

Comments: Love it. No more daily top offs!

Comments: I bought this unit about three months ago. At first like other people I was extremely worried about it staying on when I first hooked it up. But after swearing alot and doing some research I washed it off with distilled water and I then just let the sensor sit in the tanks water overnight. When I hooked it up in the morning it worked flawlessly and has ever since. I also put a little valve on the end of it to slow down the water input. To do water changes I do unplug it so it doesnt turn on but no big deal, when i plug it back it in it alway works perfect. I have a 5 gallon bucket next to the tank to hold the water and it easily lasts me almost a week! Would definately suggest spending the extra money and buying this unit

Comments: Great product. Just be careful the first few days. Like anything new that has just been placed in water, the sensor gets some bubbles form on it's surface, and the sensor thinks it's out of the water and turns the pump on. After a few days, "slime" forms and no more bubbles attach to the sensor.

Comments: I have this up and running for a couple of days so I haven't see any real, long term success as of yet but I feel this will be the ATO that will stand the test of time. There are no ridiculous suction cup or ugly hangers, just magnets. It's great! I also love the fact that it comes with 2 sensors. The sensor that controls water level isn't one of those awful float sensors that gets caked with gunk and quits working over time but an actual infrared sensor that just needs the occasional wiping. It's perfect! The second sensor makes an alarm sound when the water level is too high. It a float switch but it's made of durable plastic so there isn't need to clean or worry often on whether or not it gets stuck. I wouldn't expect any less quality from Tunze and this product is no exception. It's a breeze to set up as well! Quit wasting money on cheaper model ATO's and get a real one! It's German engineering at it's best!

Comments: This is obviously an expensive product, but overall I'm very happy with the product and performance.
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<br />Quality: quality materials. One of the attachments for the safety sensor on the magnet arrived bent (still usable), but after contacting Marine Depot they had Tunze ship me a replacement part right away. The magnet is super strong... to the point where it's almost hard to pry the 2 ends apart if you put them together (which is a good thing in my mind to keep the sensors where they need to be in the tank).
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<br />Performance: I haven't used any other ATO systems, but this one seemed to be the best, and I haven't been disappointed. The main and safety sensors work great.
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<br />The only criticism I have is it would be great if there was a on/off button on the unit. The reason is, when I put my hand in my tank the water level in the back chamber decreases, and so the system thinks it's time to top off. So I have to unplug the unit whenever I'm doing any kind of tank maintenance.

Comments: With a little bit of messing around I finally got it set up correctly. Here are 2 problems I had so that you don't make the same mistake. 1- The water level sensor is VERY sensitive. Make sure to wipe off finger print w/ vinegar, and make sure not to put the fresh water filler hose too close to it. Micro-bubbles turn it on as do finger prints. Having the overflow alarm go off at night isn't much fun. Also, make sure that when the tank is at it's highest level that the tip of the filler hose is NOT IN THE WATER. It quickly creates a syphon pulling the water out of your tank and overflowing your clean water holder thus spilling on the floor, also not fun.
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<br />Now that is dialed in it seems to be working very well though. Hopefully my experience will make yours even better.

Comments: I bought this in August 2010 but waited until now to get the full feel of this thing. Well, what can I saw other than this thing is AWESOME!!! No more letting the salinity see-saw because I forgot to top off the tank. No more worrying about the tank when we go away for a few days. The float switch and overflow alarm/shutoff work flawlessy!

Comments: Simply awesome! I've used another ATO that kept getting stuck in the "on" position with float switches and nearly flooded the fish room numerous times. I should have bought the Tunze from the start. Well worth the money and peace of mind.

Comments: This product was easy to set up and had many types of hook up mechanisms included....

Comments: Having purchased more than one of the other top off systems on the market, let me say with NO EQUIVOCATION, THIS IS THE ONLY ONE TO PURCHASE. It works better and lasts longer than any other one out there.
<br />Yes it costs a bit more, but it is well worth it.
<br />When you compare this one to others, make sure you take into account that this one includes the pump. And while we are talking about the pump, let me say it is an excelent pump.
<br />The recent improvements have made a great system even better.

Comments: The first one that I bought lasted almost 6 years in my salt water tank. When it failed it did NOT flood my tank like other units are known to do. It is the best one I have ever purchased and well worth the money. I will be replacing it with the same unit, although this new one has been redesigned.

Comments: This is a must have item for a hot summer. I was constantly having to top off both my tanks before buying this system. The install is fairly easy and takes only a few minutes. The instructions are in desperate need of a re-write! Stick with following the pictures and you'll be ok. The product itself works perfectly, as the water level stays dead-on at all times. The power connector for the pump is poor at best. I tossed it out and spliced the wires together and have had no problems at all. It's a little pricey at $192 but it's well worth it. Left for vacation for 9 days and the water & salt levels of both tanks were perfect when I returned. Overall a great item.

Comments: As in many of the reviews the product is true to form. I had no problems installing the unit and is a great quality product it does what it is supposed to do. I would recommend this product to all my friends.

Comments: First, let me quickly say that if you are thinking about buying an auto-top-off system, the Tunze Osmolator is hands down the best one out there. I've tried just about all of them over the years and I've even made two of them myself using online kits. Save yourself the headaches and start off with the best. These are soooo well designed and engineered. They are a piece of cake to position, very adjustable, and they have plenty of backup features to make sure they don't fail.
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<br />OK, so how can there be a couple of bad reviews from folks who had problems with them? Simple. Please remember that when you install the outlet tube, where the water goes into your tank or sump, that it MUST BE ABOVE THE WATER LEVEL OF YOUR WATER STORAGE TANK. If you don't mount the tube above the water level of your water tank, then you risk creating a syphon which will drain your RODI water tank even after the osmolator shuts off. This is very, very important. I strongly suspect that the folks who had problems missed this very important point. As long as you install it right, it should run headache free.
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<br />Mine have been running for several years now and they are one of my few pieces of equipment that I don't have to worry about at all.
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<br />Two thumbs up!

Comments: Very easy to set up!! Up and running in about 30min tops. Works like a charm. Extremely accurate - keeps water level constant (no more adding a large volume of RO/DI at one time each day), so osmolarity stays even, and I only have to fill up the 5gal top off container every third day for a 120gal tank. Going to set up a refugium tank with a larger reservoir for top off water so it will last a week for when I go on vacation. So far would definitely recommend this to a friend.

Comments: Easy to setup and well worth the price. THe unit works as promise.

Comments: Set and forget, I've had this unit for over a year now and my water level has never fluctuated. I have left the reservoir empty several times and it automatically stops the pump and displays a red light. Only slight drawback is the flimsy mounting equipment but it gets the job done. Expensive but you get what you pay for.

Comments: The IR sensor is more accurate than the JBJ ATO unit that was previously on my tank. Water level is far more stable. Plastic holders also allow for more fine tuning than my previous ATO. Water level audible warning is a nice feature.
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<br />Overall it's well worth the price premium over the JBJ ATO - just wish I had purchased this unit in the first place.

Comments: The good...my salinty is rock solid since putting this on. No more remembering to refill the tank morning and night. The set up is pretty easy, the hardest thing it figuring out the best way for the brackets to attach to your tank. Still only took about 20 minutes, if that.
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<br />The bad...the mounting brackets are low quality. They work fine, but I was expecting more. If you are particular about the 'clean' look, this piece will be a challenge. There is a wire for each sensor, plus one to power the unit, and a fourth to power the pump.
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<br />Overall, I'll deal with all the wires for what it does. Very happey with it.

Comments: This is a piece of equipment that I should have bought when I first set up my tank, it makes life much easier!

Comments: After reading all of the good reviews on this product i was looking forward to receiving it,However after 1 day the unit malfunctioned and overfilled my sump! The pump just comes on and stays on no matter where the sensor is positioned.There are no bubbles or ripples that could be affecting it so i believe the sensor is defective.I hope that i received a rare dud and am going to try to get replacement.wish me luck

Comments: The unit came complete with everything you need. I have the unit supplying RO/DI to my Kalkreactor which provides the makeup water to my sump. The optical sensor is very sensitive to any bubbles and ripples, and since my sump is only 10gallons it would react causing the failsafe sensor to go off. So I placed the sensor with bracket in a piece of acrylic tubing now the unit works like a charm. It is expensive but the level is always consistent. Tunze did not skimp on cable and tubing length and I would not assume for the amount of money I paid. Plus, I can call Tunze USA for any issues I have.

Comments: Overall it is a very good device. And I love it. Once it is setup it is carefree and I now can go for long vacation. The only thing that it needs to improve is to show clearly how the hardware put together. It took me quit awhile to have it setup. Also, the screws did not match the holes perfectly and I had to enlarge the holes by mechanical means. Another important thing to know is whenever the pump is lifted out of the water, you need to remember to prime the pump before its use again. Besides these, it is a great product.

Comments: This is a great product, with two sensors, well worth the money, mounting hardware is good (instructions are funky, but if you can work a screwdriver, you can mount it right). I give it three stars because the power connection to metering pump is DUMB. You MUST have the right size screwdriver, duct tape or "forcing" the cables into the connector. I left after testing the device a dozen times to return to a unit where the power cables were no longer connected (even with gorilla tape). Great unit, just make sure to double and triple check that power connection!

Comments: i purchased on of these as the reviews have been fantastic. however, on xmas eve when we came home from dinner, my sump was full and all of my fresh water was added to my tank. a real drag since i just got this thing last week. the sensor failed, and also the 10 minute shut off failed... thank god the 2nd sensor worked. i pulled it out of the system and played around with it in the sink and it was very buggered. judging by the amazing reviews everyone else has given, i am assuming i got a rare dud... i just hope to get it replaced without any problems as i already through the box away...
<br />... i will say that while it worked, it was very impressive... but my corals are very upset with the salinity drop...

Comments: The controller box is very easy to read, use and understand. The pump that comes with the unit (vs. other units needing a separate pump) is relatively quiet and is powered by the controller (one less power plug needed!)
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<br />Instructions weren't so easy to understand all the time, but with the picture examples it wasn't hard to figure out.
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<br />The sensor used to detect the water level has worked flawlessly so far, and having a backup sensor in case the water level gets too high is a great idea.
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<br />As with most Tunze products, it's pricey, but I think you get your money's worth here with Tunze's quality. It's nice to know that I don't need to worry about a mechanical float switch getting gummed up and sticking when water is needed in the aquarium!

Comments: Worth every dollar, works like a charm, I really depend upon this for top-off water on my 75 gallon saltwater tank, I just wish I would of got this sooner. Don't waste your money or time with cheaper ATO. This is the one for you.

Comments: Just installed mine yesterday and the unit appears to be working very well. The safety feature saved my butt when I accidently created a siphon from the water line (my own fault). The only downside I found with the purchase is that the instructions is a bit confusing especially when it comes to putting the mounting brackets together. I'm still not sure if it is put together like it is supposed to be but it is mounted tight onto my sump.....good enough for me.

Comments: Really precise. Have on Solana as a top off. I had trouble with it filling above the sensor and even the emergency float, but it turned out to be critters crawling in front of the intake grates to the sump. What that did was lower the level in the sump (return section)and then when the critter moved it was over full. The fix was to add a small ball valve to limit how quickly it replenishes water. Now it fills slower and the critter is usually gone before it overfills (by too much).

Comments: silent pump, has not broken down on me since i bought it (3 months) so far so good!

Comments: Great product, worth the extra money over lesser competitors. Works perfectly, safety features are great. Easy to set up. Cannot say enough good things about this product.

Comments: After standing up to the intermidating instruction I finally put all together. I took 3 months before I opened the box. The only problem is if you have the top off hose to low it siphins the water from the storage tank. Also in you have both racks connected vertically it limits the range of your sensors. It is good enough for 4 stars. Keeps water level stable.

Comments: I wasn't sure if this was worth the price. I was proven wrong! If there is one thing that will make your daily maintenance easier this is it. It is accurate, keeps my sump level perfect, allows my protein skimmer to work the most effectively, and allows me to keep an 18 gal. RO/DI water tank as the filler tank. No more daily adding water(1-2 gallons a day) I enjoy my reef tank instead of maintaining it! The overfill alarm feature allows me to sleep at night. I can now go on extended vacations and only have to have someone feed and I am assured that the tank level will remain constant. Worth the money? You be the judge, It was for me!

Comments: Works as advertised so far.
<br />I have hooked up to my 32 G topoff container that I dose with lime.
<br />We'll see how long the pump lasts as Tunze says it will shorten the life of the pump.

Comments: works quite well but need better pump that is able to expel air! If air gets into the pump in large amount (like if you let the bucket runs dry) you need to relieve the trapped air otherwise it won't pump.

Comments: Okay so I love the unit so far, only downside I saw where the directions are not that great and the cost. Once the unit is installed it seems to work good. One other thing I would mention is that the pump that refills the tank is not super quiet, you can hear it spin up....its not loud but you can hear it when it kicks off. The unit only runs for a few seconds so it does not matter. The unit came with lots of mounting options which made it very versatile. One last thing I really liked was that the motor can be easily replaced without having to send the product in.

Comments: I started with an Aquamedic Dosing Pump and the new JBJ Automatic Top-Off System. The JBJ unit would not dependably turn on the pump when the water level was low, and when it did the Aquamedic Pump would not work. What a nightmare. I fiddled around with both products for a month and finally tossed them and bought this Tunze unit. I have owned it for 4 months without a problem. The only reason I did not give it 5 stars was the initial set up. The clamping system is so adaptable to various tank configurations that it is difficult to figure out what parts to use for your specific needs. I would buy this again without hesitation.

Comments: Just what I expected from Tunze!

Comments: It took quite sometimes for the initial set up because you have to figure out what the diagrams meant. However, it has worked very nice for the last few days since I installed it. It is well worth the money.

Comments: I love this unit. It is very precise in keeping my sump level right where I need it for my Euro-Reef RS-100 skimmer. I attached both sensors into my Tidepool 2 sump. The water supply is a 2.5 gallon bucket in which the small pump is submerged. The pump looks small, but it's quiet and pumps very well. I recommend that you install with minimal pump tubing so that the pump doesn't have to push the water as far.
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<br />You receive velcro strips to attach the control unit to whatever you would like. The alarm for level warning is loud but not overbearing. You are given plenty of attachment pieces of different angles depending on how you wish to install the unit. SO don't be surprised with left over pieces.

Comments: Well Designed and love the redundancy of the float valve. Using for make up water only for sump from separate container. Make sure height of water adding is lower than outlet tube into sump or you'll get siphon drip.

Comments: great product. takes a few minutes to set up. has its quirks but it works like a charm. reasonably priced for flawless automation.

Comments: I have used this system along with the calcium dispenser for two years now, and have been very pleased with its operation. Initial setup can be a trial, because the accessory clamps and fittings don't lend themselves for attachment to typical American made tanks etc.. You will have to be creative with the collection of parts every aquarist has collected from other products. (velcro comes in handy). Overall, it's great stuff; and life's too short to spend it mixing kalkwasser and topping off your tank every day.

Comments: Mine is now one year old and is still working great. I have never had any problems with it what so ever. I highly recomend this product. It's is a must have.