Reef Octopus KS250 Nilson Kalk Reactor

The Reef Octopus KS250 Nilson Kalk Reactor is a motorized kalkwasser stirrer built for large reef systems up to 320 gallons. A high-torque, low-RPM motor gently stirs calcium hydroxide inside an airtight 10-inch acrylic chamber, so you dose clear, fully saturated limewater that raises calcium and alkalinity together and holds a stable, high pH. Pair it with Seachem Reef Kalkwasser or BRS Kalkwasser, and browse the rest of our reef additives and supplements.

Why the KS250

• High-torque stirring motor: the integrated 25-watt motor turns the mixing blade slowly and quietly, keeping the kalk in suspension without clouding the dose.
• Airtight reaction chamber: the sealed lid keeps atmospheric CO2 out, so the kalkwasser stays potent instead of carbonating and losing strength.
• Large-scale pH stabilization: saturated limewater buffers and raises pH, supporting calcification in stony corals and helping precipitate excess phosphate.
• Clean, clear dosing: undissolved particles settle at the bottom while only the clear saturated liquid at the top leaves through the output.
• 1/4-inch quick-connect fittings: push-to-connect input and output ports take standard 1/4-inch RO/DI tubing for a fast, leak-free install.
• Heavy-duty acrylic build: thick, hand-polished acrylic with oversized thumb screws for quick, tool-free access when it is time to add powder.

How It Works

Fresh RO/DI water enters the bottom of the reactor from your feed pump, rises through the bed of calcium hydroxide while the stirrer keeps it mixed, and exits the top output as clear, saturated kalkwasser that drips into your sump. The KS250 does not include a feed pump or a timer. Feed it with a dosing pump such as the EcoTech Marine VERSA VX-1 or with an auto top-off such as the IceCap ATO EZ, and run the stirring motor in short intervals on a timer or an aquarium controller like the HYDROS Minnow. The motor is rated for roughly 1,500 hours of run time, so it is designed for intermittent stirring rather than running continuously.

Specifications

What's Included

• KS250 kalk stirrer body
• Integrated 25 W stirring motor
• Power transformer (120 V to 24 V AC)
• 1/4 in quick-connect input and output fittings
• Internal stirrer arm and shaft

Recommended Pairings

• Seachem Reef Kalkwasser, calcium hydroxide powder for the reactor
• BRS Kalkwasser (Calcium Hydroxide), bulk calcium hydroxide powder
• EcoTech Marine VERSA VX-1 Dosing Pump, a precise feed pump for the reactor
• IceCap ATO EZ Auto Top-Off, for feeding the reactor with top-off water
• HYDROS Minnow Smart Controller, to schedule the stirring motor
• More saltwater and reef supplies

FAQ

Does the KS250 come with a pump? No. It ships with the reactor body, motor, transformer and fittings. You supply the feed pump (a dosing pump or ATO) and a timer or controller for the motor.

Can I run the stirrer all the time? No. The motor is rated for about 1,500 hours of operation, so stir in short intervals on a timer or controller and let it rest between cycles.

What tubing does it use? Standard 1/4-inch RO/DI tubing with the included push-to-connect fittings.

What size tank is it for? The 10-inch body is sized for large systems up to 320 gallons. Kalkwasser supplies calcium and alkalinity in a balanced ratio and raises pH, but tanks with very high demand may still need supplemental two-part dosing.