Maintain Stable Calcium & Alkalinity for Large, Demanding Reef Aquariums

When your reef reaches the point where two-part dosing becomes expensive, time-consuming, or simply can't keep up with coral growth, it's time to upgrade to a true calcium reactor.

The Reef Octopus OCTO CalReact 5000D is engineered for serious reef keepers with large SPS-dominated systems that demand rock-solid calcium and alkalinity levels 24 hours a day. Featuring a dual-chamber reverse-flow design, a powerful VarioS 6 DC recirculation pump, and premium cast acrylic construction, this reactor delivers efficient media dissolution while helping raise the pH of the reactor effluent before it returns to your aquarium.

If you're looking for long-term stability with less daily maintenance, this reactor is built to do exactly that.

Why Use a Calcium Reactor?

As stony corals, clams, coralline algae, and other calcifying organisms grow, they constantly consume:

• Calcium
• Alkalinity
• Magnesium
• Trace elements

Instead of manually dosing supplements every day, a calcium reactor dissolves natural aragonite media using controlled CO₂, returning these essential elements back into your aquarium continuously.

Benefits include:

✔ Stable calcium levels
✔ Stable alkalinity
✔ Continuous trace element replenishment
✔ Less daily maintenance
✔ Lower long-term supplement costs
✔ Excellent for heavily stocked SPS reefs

Why Choose the OCTO CalReact 5000D?

Unlike many standard reactors, the CalReact 5000D features a dual reaction chamber.

The first chamber performs the majority of the media dissolution, while the second chamber extracts additional calcium from remaining CO₂ and helps increase the pH of the outgoing effluent before it enters your aquarium.

Combined with its reverse-flow design, this increases efficiency, reduces wasted CO₂, and maximizes media usage.

Premium Features

• Dual-chamber reverse-flow reactor
• High-efficiency CO₂ recirculation
• Variable-speed VarioS 6 DC recirculation pump
• Precision effluent control valve
• Integrated bubble counter
• Built-in pH probe holder (probe sold separately)
• Heavy-duty hand-cast acrylic construction
• Quick-connect plumbing
• Easy-access removable lid
• Wet or dry installation capable
• Designed for years of reliable operation

Technical Specifications

Model: OCTO CalReact 5000D

• Recommended Aquarium Size: 423–608 gallons (1,600–2,300 L)
• Reactor Type: Dual Chamber
• Flow Design: Reverse Flow
• Media Capacity: 15.2 L (4 gallons)
• Reactor Diameter: 7.9 inches
• Footprint: 18.1 × 15.2 inches
• Height: 22.9 inches
• Inlet/Outlet Size: ¼ inch
• Suggested Feed Pump Flow: 132–211 GPH
• Recirculation Pump: VarioS 6 DC
• Maximum Pump Flow: 1,720 GPH
• Maximum Head Height: 16 feet
• Pump Power: 70 Watts
• Installation: Wet or Dry
• pH Probe: Not Included (holder provided)
• Reactor Media: Sold Separately

Ideal For

• SPS-dominated reef aquariums
• Mixed reefs with heavy calcium demand
• Large reef systems over 400 gallons
• Reef keepers replacing daily dosing systems
• Aquarists looking for long-term stability and automation

What's Included

• OCTO CalReact 5000D Reactor
• VarioS 6 DC Pump
• Bubble Counter
• CO₂ Check Valve
• Effluent Control Valve
• Inlet/Outlet Valves
• Plumbing and Fittings
• O-rings and Hardware

CO₂ system, pH controller, pH probe, reactor media, and feed pump sold separately.

Why Buy From Infinity and Beyond Aquatics?

When you order from us, you're buying from fellow hobbyists who understand what it takes to keep a successful reef aquarium.

✅ Authorized products from trusted manufacturers

✅ Carefully packaged for safe delivery

✅ Free Shipping on qualifying orders over $100*

✅ Friendly customer service from hobbyists who actually use the equipment we sell

Whether you're building your dream SPS reef or upgrading an established system, we're here to help every step of the way.

Shipping Information

FREE Shipping Included
This oversized item ships FREE within the contiguous United States.

Please allow up to 3 business days for order processing before your order ships. Business days do not include weekends.

Shipping times and delivery speeds may vary depending on the warehouse location fulfilling your order and your delivery address. Orders containing multiple items may arrive in separate packages.

Once your order ships, tracking information will be sent to the email address provided at checkout.

Thank you for shopping with Infinity and Beyond Aquatics!