Best Calcium Reactor (GUIDE and REVIEWS)

Adding a calcium reactor is an effective approach to supply calcium to a reef aquarium.
Let’s see why it is an important addition for your reef tank and what the best calcium reactor picks are.
Let's dive in.

Corals and other reef-building marine life thrive only when their environmental conditions support their growth.
These conditions include proper lighting, temperature, nutrition and water quality.
Stony or “reef building” corals are comprised of individual polyps that form a coral colony.
Reef-building corals grow in a wide range of shapes and sizes.
Small polyp stony (SPS) Acropora coral form branching colonies.
Montipora coral forms a non-branching plate-like structure. Large polyp stony (LPS) Euphyllia corals have a fleshy appearance.
Coral reefs form as the coral colonies secrete calcium carbonate.
The calcium and carbonate is extracted from the seawater and converted into dense calcium carbonate (CaCO3).
This forms the skeleton upon which the polyps grow and spread out, forming a solid living rock structure.
In the reef tank calcium and carbonate (KH) levels must be monitored and maintained so the corals have adequate “building materials” to create the reef.
This involves testing the aquarium water for calcium and carbonate (KH), and adding the right amount of calcium and carbonate supplements to the water.

But don’t confuse a calcium reactor with a media contactor. Media contactors simply hold filtration media in a chamber for better water contact.
Calcium reactors isolate a unique chemical reaction from the main aquarium.

A calcium reactor consists of a reaction or contact chamber filled with solid granular calcium carbonate-based media.
Aragonite is a natural, calcium-rich media commonly used in reactors as a source of calcium and carbonate.
Aragonite and other types of calcium reactor media dissolve too slowly on their own to keep up with calcium demand.
It takes an acidic environment to cause the aragonite to break down into soluble calcium and carbonate.
To create slightly acidic conditions, carbon dioxide gas is injected into the reaction chamber.
Carbon dioxide dissolves in water and forms carbonic acid.
The weak acid slowly dissolves the aragonite media.

You’ll have to provide a bottle of compressed carbon dioxide and gas regulator for injection into the reactor.
Some aquarists use a pH meter and controller to monitor the pH inside the reactor.
The chemical reaction that releases the calcium needs to be at a pH range of 6.5 to 6.8.
The pH meter monitors the pH level inside the reactor.
If the pH gets too low or too high, the controller turns the carbon dioxide gas flow on or off, with an electric solenoid valve.
This automated system requires a pH meter with on and off power switching and a gas solenoid valve.
The initial start-up cost is higher than manual testing and addition of calcium and carbonate supplements.
The benefits are long-term stability in pH and calcium levels.
This translates into a more stable reef environment.
The end result is healthier, highly-colored SPS and LPS corals.

The ViaAqua AC10 Acro-Cal calcium reactor is rated for reef aquariums between 10 and 75 gallons.
The reaction chamber is mounted externally on the back of the aquarium or inside a filter sump.
Water is fed to the reactor either through gravity from the aquarium, a T from an existing return pump line or with a stand-along submersible water pump.
Carbon dioxide is released into the Acro-Cal from your pressurized carbon dioxide tank.
A bubble counter is included for visual CO2 adjustment.
If you want to monitor the pH and control the carbon dioxide gas flow with a solenoid valve, a compression fitting is located on top of the reactor.
This allows a pH probe to be inserted into the chamber for pH monitoring.
The ViaAqua AC10 has its own internal circulation pump, built into the top of the reactor.
The internal pump ensures the acidified water is constantly moving throughout the aragonite media.
A set of three valves on top of the reactor are used to regulate the water flow through the reactor as well as venting air out of the chamber.
The reactor measures 15 inches in height and 4 inches wide.

Reef Octopus is known for their high-quality protein skimmers.
The VarioS calcium reactor uses the same high-quality components as the skimmer units.
Rated for medium to large reef aquarium up to 150 gallons, The VarioS CR140 is capable of supplying densely-stocked corals with plenty of calcium.
The CR140 has a larger footprint due to its size and external water pump.
The pump is mounted to the side of the cast acrylic reactor and takes up more space.
The reactor uses a low-voltage DC water pump.
The multi-speed pump makes it easy to control the water flow through the reactor.
The VarioS DC water pump features a pinwheel impeller, a detachable controller, high quality ceramic shaft and bearing to reduce wear and tear, and the latest variable speed flow technology.
The reactor is APEX-compatible for use in automated aquarium set-ups. The CR140 includes a built-in bubble counter and port for a pH probe.
The unit has a height of 23 inches.
It holds up to one gallon of reactor media.
The VarioS CR145 is designed to sit inside a filter sump.

Built with a similar design to the smaller ViaAqua AC10, AC30 Acro-Cal calcium reactor is rated for 50 to 200-gallon reef aquariums.
The AC30 is 22.75-inches tall and 5.5-inches wide.
This model can be hung on the aquarium or placed in the sump.
The height may make operation adjustments difficult inside an aquarium stand or cabinet.
The sponge discs stabilize the aragonite media and ensure an even flow distribution through the granular media.
The AC30 uses the same inlets and outlets as the smaller AC10.
Fine-control valves make adjustments easier.
A compression fitting is included so you can use a pH meter and controller to regulate the flow of carbon dioxide inside of the reactor.
A separate bubble counter is included and is used to confirm carbon dioxide gas is flowing.

Larger reef aquariums with dense a dense SPS and LPS coral load need a constant supply of calcium to keep the coral colonies growing.
The VarioS CR 200 is designed for large reef tanks up to about 500 gallons.
The reactor measures 8-inches across and 23-inches in height.
The cast acrylic reactor holds two gallons of aragonite media.
The VarioS CR-200 has a large footprint, measuring 15.2-inches by 10.6-inches.
This partly due to the external Reef Octopus VarioS 4 direct current (DC) water pump.
The water pump operates on low-voltage DC current, which is safer around water, drips and spills.
The water pump comes with a controller to fine-tune the pump speed.
This makes adjusting the water flow rate through the reactor easier and more precise.
The Various 4 water pump is very quiet and uses very little energy. The maximum flow rate through the reactor is 150 gallons per hour.
A built-in bubble counter makes monitoring carbon dioxide flow easy.

A calcium reactor is considered a necessity by serious reef aquarists.
The stability the reactor creates by supplying a continuous supply of calcium and carbonate improves the water chemistry and provides corals with reef-building elements.
All of the calcium reactors we reviewed are top performers made by reliable companies.
The ViaAqua reactors are simple to set up and effective.
You’ll have to connect a water supply or additional pump to run it.
Reef Octopus comes with single a DC water pump for plug and play operation, ease of fine tuning and compatibility with APEX aquarium automation systems.
Take a good look at both systems and decide which one is right for your reef aquarium.

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