Looking for DIY auto topoff/kalkwasser plans


New member
I'm interested in creating an automated top off system for my 75 gallon mixed reef...planning to buy a double switch sump mounted controller from autotopoff.com but need ideas on how best to incorporate kalk topoff into my system...or is it better/safer just to do this separately? I have to admit I am very leary of pursuing kalk topoff because of the stories I've heard where people lose their entire tank to an overdose of kalkwasser.


New member
One of the safest methods I have seen for running Kalk is to use a Aqualifter pump to draw (drip) from a bucket of premix. The bucket would only contain a "as needed" amount of saturate, and the Aqualifter was set on a basic timer allowing you to dial it in as needed. Its a little more effort on your part to mix and refill the bucket...but much safer than running it through your ATO.

I would still recommend you purchase the ATO. But just use it for regular freshwater topoffs.


New member
With the dual switches (failsafe) you should never have an overdose of kalk reach your system.

I have been running the dual switched ATO from autotopoff.com in conjunction with a Aqualifter and GEO Kalk reactor with no problems what so ever. The only time I ever overdosed was when I only ran a single, un shielded, switch in the sump, and it got stuck on a floating grain of carbon. I was home at the time and was able to save the tank and its inhabitants with a major water change (60%), two days in a row. Also, the danger was not only the kalk overdose, but a sharp, and extreme reduction in salinity.

This is very consistent, very dependable and extremely easy to setup. The danger you face in mixing your own effluent is consistency. Not to mention the extra maintenence.


New member
I am going to be using the dual float switch from autotop off and hooking up my ATO to a Kalk Stirrer, but I am hooking it up to my ACjr so I can monitor the PH and turn it off if the PH gets too high. I am also only going to run the ATO after the lights are out to keep the PH more stable in the tank.

I think running Kalkwasser with an ATO without some form of controller is a disaster waiting to happen.



aka John K
One of the safer ways to do it is to get a peristaltic pump that will pump a little less than the total volume of evaporation in a given time.

For example, My system evaporates about 3.5-4.5 gal / day. I run dose kalk with a pump that moves about 3 gal if run 24/7. The difference is made up with straight RODI on a traditional ATO.

Also, if your going to run a kalk reactor/stirrer, you can usually have the pump pumping straight RODI into the reactor, thus pushing kalk mix out. This way the pump doesn't get fouled up with the kalk.


Premium Member
Here's how I do mine:

My top off water comes from a reservoir on the ground floor ( laundry room ).

My sump is in the basement ( directly beneath the laundry ).

It feeds a Float valve that keeps the water level in my sump constant.

I also have a Kalk stirrer that sits above my sump on a shelf.


I tee off the RO/DI line that feeds the float valve and run it INTO the kalk stirrer via a JG needle valve.

I adjust the drip from the Kalk stirrer to "try" to just put in enough to make the float valve never open.

Obviously I err on the side of less is better and the float valve takes up the slack.

I typically check it daily and "tweak" it based on the relative humidity.