Kalkwasser Stirrer / Reactor 300 - Two Little Fishies

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Kalkwasser Stirrer / Reactor 300 - Two Little Fishies

80% Recommend this to a friend (8 of 10)

SKU: 207226

reg. $85.14

Special Price: $72.37

In Stock: 18
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Quick Overview

Designed with an upflow principle to achieve the most efficient use of Kalkwasser. Mount on the back of your aquarium or below your tank. Includes check valve and flexible connection fittings that rotate 180° to suit your installation.


  • Height: 15.25"

  • Width: 5"

  • Reactor Diameter: 4"


Full Details

Two Little Fishies Kalkwasser Stirrer/Reactor has a patent-pending design by Julian Sprung. Uses upflow principle to achieve the most efficient use of Kalkwasser. By pushing top-off water upward through the calcium hydroxide, it automatically mixes it to achieve a supersaturated kalkwasser solution.


  • Very convenient design that can be mounted hanging on the back of the aquarium or below the aquarium.
  • Includes check valve and flexible connection fittings that rotate 180 degrees to allow a perfect custom fit to your installation.
  • Threaded lid design makes adding calcium hydroxide or servicing quick and easy.
  • Model 300 for aquariums up to 300 gallons.


Approximate Footprint:

  • Height: 15.25"
  • Width: 5"
  • Reactor Diameter: 4"
  • Inlet/Outlet: 1/2 inch


Inlet and outlet elbows allow for 180° rotation to suit your needs


10 Items

  • running it with tunze ato By dbh on 8/31/2014

    Seems to be working great with my tunze ato. My ato only runs 14 seconds at a time 2-3 times an hour. If your going to run your two little fishies kalkwasser reactor in this way than you will need to buy the tunze switched plug so you can run a larger pump 200-300 gph. I recommend either a cobolt mj 1200 or a rio 4hf. I'm using the Rio and everything is good. Because it only runs for 14 seconds at a time I don't have to worry about the saturated slurry entering my tank. Make sure that if your doing mantince on your tank that will cause water levels to drop. That you turn off the ato or it will overdose your tank.
  • Decent if you have small tank and small budget By Rob on 2/27/2014

    I bought this little reactor for my 55 bowfront thinking it would be great and I guess it is for the money. Setup is critical to good results.

    A) Don't put too much kalk in. Keep kalk below the little spinny jet or it will get plugged.

    B) Use a low flow pump to avoid stirring up too much kalk

    C) Pray your check valve is functioning or it will back siphon into your top off container.

    D) Make sure you place it as close to the same level as your top off container as possible.

    E) Don't run it for more than a few seconds at a time or you will blow kalk into your tank. Top off more frequently (I use reefkeeper) A small pump really helps here too to keep you from over stirring.
  • You get what you pay for. By Quinnchero on 12/18/2013

    Heading says it all. This is a very cheaply made product.....that actually works though. Like a few of the previous posters have stated you have a very short window of time before the truly saturated Kalkwasser water is pushed out and the Kalk itself is being sent into the system, which is NOT a good thing to happen.
    Side note here: I searched for this information for quite some time on a large number of sites with no success: IT WILL NOT WORK WITH A LOW FLOW ATO SYSTEM ie. ToM Aqualifter pumps which many use for their slow ATO systems. You will need a minimum 200GPH pump.
  • Love it..works great on my 120 By Budman on 8/15/2013

    I use to drip kalk outta 1 gallon container and really got tired of making it every other day so 6 months ago go I got this unit and I'm so pleased with it,especially for the price.It keep my levels in check and probably fill it with new kalk every 2 weeks,Great unit for the price and would recommend to everyone..
  • great buy By Robert on 4/4/2013

    I think this much better than the motor driven reactor. Great Buy
  • You get what you pay for By MHG on 3/10/2013

    I bought this aver a year ago from BRS. At the time I liked it but I found it has a few issues.... It does a poor job at stirring the kalk as the days go on. It does fine when you first add kalk. It starts to solidify on the bottom and the stirrer needs maintenance often to keep it spinning... You only get about 50 seconds of pumping top off water through it before it starts blowing kalk into your tank. That is using a maxijet1200. It needs to run about once an hour to keep up with my 60 gallon tanks evaporation rate. But you can not run it more as the kalk needs time to settle. This is going to be an issue on bigger tanks...

    I would imagine a motorized stirrer would get more efficient use but at the price you pay for this unit it is ok I guess. The one great feature is how easy it is to add kalk. Just make sure you do it right after the unit pumps so the new kalk has time to settle...
  • Life is easier By cdbstl76 on 3/4/2013

    I previously had a ATO set up. I also had a home-made drip system for my Kalwasser. Now, I have them combined! I didn't care much for the fact that due to it's size, mounting options are greatly limited! Pay attention to the height and depth needed for this product. I could not mount it where I had initially planned, due to poor planning. However, once a new solution was derived, I couldn't be happier. Now, every time my ATO kicks in, I get a little dose as well. I will have to keep an eye on my levels and may have to adjust accordingly due to amount of top off that enters my system daily. But, this is so much better than my previous delivery method!
  • Great deal but be careful adding more kalk By Gregory on 10/22/2012

    This thing is pretty sweet for the money. Simple yet effective solution that works well when you follow the directions and only add 1/2 cup of kalk at a time. For my tank, that lasts a couple of weeks since I have really low evaporation. Before adding another 1/2 cup of kalk to the reactor through the top, make sure you dump at least a half a cup of the effluent out into another container first, or you'll increase the effluent level in the reactor with the fresh kalk powder, and it'll start dosing out the kalk powder you just put in!! Talk about a pH spike...
  • Nice Reactor By Sean on 1/31/2012

    I was tired of mixing kalk manually in another container so I decided to give this a try. I figured for the price why not. I have to say I have been pleased. As long as you don't put too much kalk in it works perfectly.
  • Good for thre $$$ By Mark on 10/15/2011

    Well this is the first reactor I purchased (aside from the BRS GFO I purchased at the same time). It is built as one would expect for $65. Lots of thin lightweight plastic. That is not to say I am disappointed with it. I like its ease of set up. It is clean and easy to replenish the kalk. No water to mess with. Easy to install…

    You only get about 1 minute of run time before the kalk dust is stirred up to the top. That means setting your ATO to top off many times a day to keep up with evaporation.

    Still, I would recommend it as for the money it can’t be beat...


Ask a question

Product Questions

Does this work well with Tunze Osmolator?
Question by: anthony on Nov 16, 2017 1:10:00 PM
The TLF Kalk Stirrer has 1/2" input and output fittings and maybe a little difficult to adapt the osmolator tubing to work with the fittings on the reactor. You may want to look into an ATO that has a pump with 1/2" tubing, or a stand-alone controller like the JBJ ATO and add on a Cobalt MJ900 with a Two Little Fishes barbed ball valve.
Answer by: Charlie (Admin) on Nov 18, 2017 8:03:00 PM
I'm using this reactor inline with my ATO and its doing a great job of keeping my ph high and stable. There currently is quite a bit of Kalk in the bottom (as designed I believe), I'm not sure when I need to clean out what's in there and put in fresh kalk. Any suggestions? Should I just wait until my ph stops being as constant? I'd like to be proactive about it if I can.
Question by: Brett Moore on Jun 8, 2016 10:47:00 AM
Great question!
This is something we typically clean out on a monthly scheduled cleaning. Feel free to let us know if you have any further questions.
Answer by: Connor (Admin) on Jun 9, 2016 7:16:00 PM
This reactor does not drip. So how many times should I turn it on and for how long should I let it pour in the sump on a daily routine.
Question by: Dannie on Mar 17, 2014 10:53:00 PM
Hi Dannie,
Its meant to be hooked up inline on your auto top off system. That way your auto top off just adds a little bit all day as water evaporates. If not using it that way, you want to use a very slow pump (like an aqualifter) and run it frequently for very short bursts (to avoid a spike in pH) as necessary to keep up with your calcium and alkalinity needs. Test your parameters over the coarse of a week and if they go down, you need to add a bit more and vice versa.
Answer by: Bulk Reef Supply on Mar 17, 2014 10:53:00 PM