Two Little Fishies

Kalkwasser Stirrer / Reactor 300

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Discontinued by Bulk Reef Supply
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Two Little Fishies Kalkwasser Stirrer/Reactor has a patent-pending design by Julian Sprung. Designed with an 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. 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. 



  • 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
More Information
UPC 748172423004
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Product Questions

Does this have a hang on back bracket?
Question by: Daniel de Gula on Apr 4, 2024, 10:42 PM
Yes but this has been discontinued
Answer by: Tyler Schafer (BRS Staff) on Apr 10, 2024, 10:01 AM
Could this be used with a dosing pump? I was thinking about using a Kamoer x1
Question by: william TYSON on Apr 13, 2020, 8:21 PM
Hi Tyson,

I would not recommend the X1 or any other non-continuous duty peristaltic pump for use on a kalkwasser reactor or ATO. The main reason for this is the fact that these pumps are not designed to move large volumes of water. They are also not designed to create the flow needed to stir the kalkwasser in a reactor like this one.
If you are set on using a perstaltic pump I would recommend going with the Kamoer FX-STP, the Neptune DOS, or the EcoTech Versa.

I hope this helps!
Happy Reefing

Answer by: Nick on Apr 20, 2020, 1:18 PM
How much water will this reactor hold?
Question by: Axle Davis on May 3, 2019, 6:42 PM
Hi Axle, this reactor will hold approximately a half gallon of water.

Please let me know if you have any further questions.
Answer by: Matt on May 6, 2019, 11:30 AM
Does this work well with Tunze Osmolator?
Question by: anthony on Nov 16, 2017, 1:10 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 on Nov 18, 2017, 8:03 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 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 on Jun 9, 2016, 7:16 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 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 PM