If you want a precision auto top off device. You need to check out the Tunze Osmolator. This thing is tough. It’s something I have come to expect from Tunze engineering. Your not going to have to worry about your aquairum ever losing water again with this baby. Why is that?
The most important thing to remember about your aquarium. Your aquarium is only as healthy as the water you put in it. The better the water, the better your aquarium will do. I highly suggest an RO/DI filter at least a 5 stage with genuine Dow FilmTec membranes. These are the best that you can buy.
Anyways back to the topic at hand. I have my RO/DI unit underneath my bathroom cabinet. As seen in the picture:
From there it goes to the left thru a wall and into my fish room.
Then from there it goes into my holding tank for pure RO/DI water. This is where the Tunze Pump is located along with a cylinder from my Kalkwasser Top off.
From there the Tunze System takes over. The nicest part of the Tunze system is that it uses an optical sensor. Optical sensors are far more reliable than float switches which is used in most of the cheaper auto top off systems out there. The reason is simple, they are just more reliable. When the Tunze system detects the my sump running low on water via the optical sensor, the pump that is residing in the holding tank click on and start pumping water into my sump. When the optical sensor senses that the water level is met the pump then clicks off. And your have your normal water levels. This is a very simple system.
In closing there is nothing on the market that even comes close to the precision of this unit. However, I have heard of some complaints that the optical sensor gets covered with “salt creep”. This isn’t the case if you have proper flow going thru your return section of your sump. I mounted the device holder with silicone to my acrylic sump. You also have the option of mounting the Tunze Osmolator directly inside your aquarium, I did not choose this route as I wanted as little clutter as possible inside my aquarium.
The only thing I could see room for improvement is the fact that its very hard to install if you don’t have a sump that is like the example they show you in the instructions or unless you do the dab of silicone glue route like I did. Other than that, this unit is expensive ($175). My rating 4 out of 5 stars.