Reef Octopus

CR100 4" Calcium Reactor

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$314.49 $369.99

Discontinued by Bulk Reef Supply
- +

Maintain the calcium and alkalinity in your reef tank with CR100 Calcium Reactor from Reef Octopus.

  • Rated for aquariums up to 150 gallons
  • Reverse flow and CO2 recirculating design
  • Aquatrance 1200 Pump
  • pH probe holder included (probe sold separately)


A calcium reactor is used to maintain a balanced amount of calcium and alkalinity in your reef tank. In order to use a calcium reactor, you will need a CO2 regulator, CO2 tank, pH probe/controller, small feed pump (flow rate should be set 1-2 liters per hour) and calcium reactor media.


Filtration Handling

Well Stocked Tank - Rated up to 90 gallons

Medium Stocked Tank - Rated up to 125 gallons

Light Stocked Tank - Rated up to 150 gallons



  • Reverse flow design
  • Control the reactor with CO2 needle valve and the effluent valve
  • Auto fill bubble counter
  • pH probe holder
  • Easy to remove lid
  • Precision effluent control valve
  • Solid construction
  • 1/4" quick connect fittings


Reactor Specifications:

  • Body Size: 4”
  • Foot Print: 9.5” x 7.5”
  • Total Height: 20”
  • Media Capacity: 1.7L
  • Inlet Size: 1/4"
  • Max Feed Rate: 150 GPH
  • Suggested feed rate is slightly higher than a full flowing influent


Aquatrance 1200 Pump Features:

  • Quiet operation
  • Power Consumption: 15 Watts


Manufacturer's Warranty

  • 1 year on pump
  • 1 year on reactor body
More Information
UPC 6950291210432
Media Capacity 2 Cups / 473mL, 3 Cups / 710mL, 4 Cups / 946mL
Reactor Placement External, In Sump
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Product Questions

Looking at your catalogue picture, I don't see the inlet for the ph probe. The description says it has one, but I don't see it. All I see is two inlet/outlets.
Question by: John 2 on Nov 7, 2021, 10:15 AM
The pH probe holder is at the top next to the two inlet/outlets.
Answer by: Matt Lucero (BRS Staff) on Nov 8, 2021, 11:56 AM
Is this unit internal or external and why isn't t indicated in the description ?
Question by: Troy Dean on May 15, 2016, 2:43 PM
Great question!
The design of all calcium reactors will be internal or external however you need. They are all sealed off containers and can be in the sump or run externally as needed.
Answer by: Connor on May 17, 2016, 8:46 PM