Calcium Reactor

Updated August 12, 2019
Author: Mike - FishLore Admin
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The calcium reactor is sometimes referred to as a kalkreactor, kalkreaktor, or even just a lime reactor. Although many other hobbyists have developed DIY versions of these reactors, Daniel Knop is often credited with producing the first commercial unit.

calcium reactor

If you have a reef tank setup you're going to be getting into maintaining your calcium and alkalinity levels. Keeping these levels up where they need to be is very important for the growth of your corals. There are several ways to keep the calcium and alkalinity levels up in your reef tank, including:

Each of these calcium dosing options have their own pros and cons. Using supplements can get expensive, especially if you have a very large reef tank. Dosing with kalkwasser can raise the aquarium pH to dangerous levels if not added correctly and a calcium reactor can be quite expensive initially to set up.


What is a Calcium Reactor

A calcium reactor is a piece of aquarium equipment that allows you to semi-automate the addition of calcium to your reef tank. Connected to the aquarium, it works by pumping CO2, Carbon Dioxide, into a chamber containing a calcium carbonate substance and saltwater. The CO2 lowers the pH in the chamber and dissolves the calcium carbonate thereby releasing calcium, minerals and trace elements into the connected aquarium. Using a calcium reactor may actually be more beneficial because not only does it raise the calcium and alkalinity levels but it also adds minerals and trace elements into the tank as well.

This sounds really neat. What all do we need to get one of these reactors running you're wondering?

Equipment Needed

To dissolve aragonite based media it is commonly recommended to run the pH in the reactor chamber in the low to mid 6 range (6.1 - 6.5 pH).

How Much Will This Cost?

It depends. If you're a Do It Yourselfer you could save some money setting up a DIY reactor. If you're mechanically challenged (like me) then buying these components and hooking them all up is the way to go, albeit more expensively. Look for deals online at the major saltwater aquarium equimpent stores and on ebay. You could find a good deal on all the equipment you need.

Using a calcium reactor for a smaller (say less than 55 gallons) could take awhile to recoup the initial purchase price of all this equipment. If you're running a larger reef tank though, a calcium reactor will definitely save you money and be potentially less labor intensive than dosing calcium, alkalinity and trace elements manually. Even a tank full of growing corals should have their calcium needs adequately met with a calcium reactor.

Calcium Reactor Setup

Although we'd love to give steps on how exactly to set yours up, there are many different reactors out there. Nor can we tell you what CO2 bubble rate or flow rate on the output that you should use. It depends on the calcium demands in the system, size of the aquarium, etc. Start off slowly, test and then tweak your bubble rate until you get the levels you need. It should go without saying, but you need to have alkalinity and calcium test kits to monitor these parameters. Keep a chart in microsoft excel of your test readings (while holding off on dosing) over a period of two weeks or so and you can get a good idea of the calcium and alkalinity demands of your system.

Watch the video below for more information on the calcium reactor and what you will need to set one up.

Calcium Reactor Tips and Comments

From: Dave
Make sure you test the "effluent" which is the water coming out of the reactor for dissolved phosphates. As the media dissolves it can sometimes release phosphates which can give you algae problems.
Thanks for the tip Dave. If you do have phosphates in the outflow you could try to offset it by running the effluent through an attached refugium first. Any growing macro algae might help remove the phosphates.