Comments: I have had this item and the Tunze top off system for three years. It is well made, reliable and the design is sophisticated. The only drawbacks are:
<br />1. Other reviewers are correct. It would benefit from some sort of stirring mechanism. I'm toying with the idea of fitting a small pump activated by a timer to stir the contents briefly once a day.
<br />2. It is important to keep the optical water sensor clean. this is mentioned in the directions, but one's memory can fail. The back-up high level sensor will save you, but it too should be periodically checked for proper operation.
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Comments: I bought this as an easy way to dispense Kalkwasser in conjunction with the Tunze Osmolator topoff unit I purchased. Basically, water enters the dispenser from the bottom, and water exits into your sump/tank thru the top.
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<br />After about a week I took mine out and bought a Kalkwaser stirrer instead for a lot more money.......the issue? My tank is an SPS type reef and it uses a lot of calcium..so this product was not up to the task. I believe that this would work well in an LPS, mixed (Soft/LPS), or soft coral type tank where the rate of calcifiction is less.
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<br />Anyone wanna buy a slightly used kalkwasser dispenser?

Comments: As the person stated above, the check valve is bad. I was pulling the tubing off and the thing broke. Nothing a little super glue couldnt fix but still. Also the valve doesnt kick in sometimes emptying some of my rich Kalk into my top off water.
<br />If I could have done it over again, I would just have bought the PM Top off with the MaxiJet stirrer.
<br />The way this dispenser mixes the KALK is not good enough. I end up shaking the canister on a daily basis to get a good mix with the kalk.
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<br />If I dont manually mix it, my calcium/alk drops from 400-420 to 350... and alk from 10 to 8.5 by the end of the week.
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<br />I recommend this to those if they are on a budget. I was at the time of buying this.