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  • Reef Octopus Nilson Kalk Reactor
  • Reef Octopus KS100 Nilson Kalk Reactor, 4-inch acrylic kalkwasser stirrer with 15 W motor and transformer
  • Reef Octopus KS150 Nilson Kalk Reactor, 6-inch acrylic kalkwasser stirrer with 20 W motor and transformer
  • Reef Octopus KS250 Nilson Kalk Reactor, 10-inch acrylic kalkwasser stirrer with top-mounted 25 W motor
  • Reef Octopus KS250 Nilson Kalk Reactor cutaway diagram showing bottom input, top output, stirrer shaft and motor
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  • Sku: OCT-KS100
  • Vendor: Reef Octopus

Reef Octopus Nilson Kalk Reactor

$392.69 USD
Shipping calculated at checkout.
Model: KS100 (up to 120 gal)

Product description

The Reef Octopus Nilson Kalk Reactor is a motorized kalkwasser stirrer that turns calcium hydroxide powder into clear, fully saturated limewater and doses it into your sump on your schedule. A high-torque, low-RPM motor keeps the powder mixed inside an airtight acrylic chamber, so your kalkwasser stays potent instead of carbonating in an open bucket, and your tank gets calcium, alkalinity and a stable, high pH from one simple device. Three sizes cover reef tanks from nano-plus systems to 320 gallons. Pair it with Seachem Reef Kalkwasser or BRS Kalkwasser, and browse the rest of our reef additives and supplements.

Three sizes, one design. Every KS reactor uses the same sealed stirring chamber, the same 1/4 inch quick-connect plumbing and the same 24 V stirring motor. Pick the body size by your tank volume and how much kalkwasser it consumes.

How It Works

Fresh RO/DI water from your feed pump or auto top-off enters the bottom of the reactor, rises through the bed of calcium hydroxide while the stirrer keeps it in suspension, and leaves the top output as clear, saturated kalkwasser that drips into the sump. Undissolved particles settle at the bottom, so only clear solution reaches the tank. The motor runs in short intervals on a timer or controller rather than continuously, which keeps the powder fresh and extends the motor's life.

Features, All Models

High-torque stirring motorA low-RPM motor turns the mixing blade slowly and silently so the kalk stays suspended without clouding the dose.
Airtight reaction chamberThe sealed lid keeps atmospheric CO2 out, so the kalkwasser holds its strength between refills.
pH stabilizationSaturated limewater raises and buffers pH, supporting calcification in stony corals and helping precipitate excess phosphate.
1/4 inch quick connectsPush-to-connect input and output fittings take standard RO/DI tubing for a fast, leak-free install.
Heavy-duty acrylicThick, hand-polished acrylic built for a saltwater environment, with a wide base for stability in the sump area.
Tool-free refillsOversized thumb screws release the seal-tight lid so adding powder takes seconds.

Choose Your Size, Model Comparison

Select a model in the tab section below for the full individual spec sheet.

Spec KS100 KS150 KS250
Rated aquarium size Up to 120 gal Up to 210 gal Up to 320 gal
Body diameter 4 in 6 in 10 in
Footprint 5.5 x 5.5 in 7.7 x 7.7 in 12.6 x 12.6 in
Total height 27.6 in 26 in 26 in
Stirring motor 15 W 20 W 25 W
Kalk powder capacity 90 to 120 g 120 to 150 g 150 to 180 g
Fittings 1/4 in quick connect 1/4 in quick connect 1/4 in quick connect
SKU OCT-KS100 OCT-KS150 OCT-KS250

Detailed Model Specifications

Click a model below to view its full specification sheet.

KS100 · 4 in body · up to 120 gal · 15 W

The compact KS100 fits a tight sump cabinet with a 5.5 inch footprint and holds 90 to 120 grams of kalk powder, enough to keep a mixed reef in the 80 to 120 gallon range topped up with saturated limewater.

Specification Value
SKU OCT-KS100
Rated aquarium size Up to 120 gal (300 to 500 L)
Body diameter 4 in (100 mm)
Footprint 5.5 x 5.5 in (140 x 140 mm)
Total height 27.6 in (700 mm)
Stirring motor Integrated 15 W high-torque, low-RPM motor
Kalk powder capacity 90 to 120 g
Power supply 120 V AC to 24 V AC transformer (included)
Input / output 1/4 in quick-connect fittings for standard RO/DI tubing
Construction Hand-polished acrylic body, thumb-screw lid
Requires Feed pump (dosing pump or ATO) and a timer or controller, sold separately
Warranty 1 year on the reactor body

KS150 · 6 in body · up to 210 gal · 20 W

The mid-size KS150 steps up to a 6 inch chamber and 120 to 150 grams of powder for reefs in the 130 to 210 gallon range, still on a 7.7 inch footprint that slides beside most sumps.

Specification Value
SKU OCT-KS150
Rated aquarium size Up to 210 gal (500 to 800 L)
Body diameter 6 in (150 mm)
Footprint 7.7 x 7.7 in (195 x 195 mm)
Total height 26 in (660 mm)
Stirring motor Integrated 20 W high-torque, low-RPM motor
Kalk powder capacity 120 to 150 g
Power supply 120 V AC to 24 V AC transformer (included)
Input / output 1/4 in quick-connect fittings for standard RO/DI tubing
Construction Hand-polished acrylic body, thumb-screw lid
Requires Feed pump (dosing pump or ATO) and a timer or controller, sold separately
Warranty 1 year on the reactor body

KS250 · 10 in body · up to 320 gal · 25 W

The KS250 is the large-system reactor: a 10 inch chamber holding 150 to 180 grams of powder for SPS-dominant and commercial displays up to 320 gallons, where kalkwasser demand runs highest.

Specification Value
SKU OCT-KS250
Rated aquarium size Up to 320 gal (800 to 1200 L)
Body diameter 10 in (250 mm)
Footprint 12.6 x 12.6 in (320 x 320 mm)
Total height 26 in (660 mm)
Stirring motor Integrated 25 W high-torque, low-RPM motor
Kalk powder capacity 150 to 180 g
Power supply 120 V AC to 24 V AC transformer (included)
Input / output 1/4 in quick-connect fittings for standard RO/DI tubing
Construction Hand-polished acrylic body, thumb-screw lid
Requires Feed pump (dosing pump or ATO) and a timer or controller, sold separately
Warranty 1 year on the reactor body

Which Size Is Right for You?

KS100: reef tanks up to about 120 gallons, or any system where cabinet space is the limit. Its 4 inch body is the easiest to tuck into a small sump area.

KS150: the sweet spot for 130 to 210 gallon reefs and for mixed tanks growing into SPS, with more powder capacity between refills.

KS250: large SPS-dominant displays and multi-tank systems up to 320 gallons, where a smaller reactor would need refilling too often to keep up.

Setting Up Your Reactor

None of the KS reactors include a feed pump or timer. Feed the input 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 on a timer or an aquarium controller like the HYDROS Minnow. Fill the chamber most of the way with RO/DI water, add powder within the capacity listed for your model, and stir in short intervals a few times a day rather than continuously. The stirring motors are rated for roughly 1,500 hours of run time, so intermittent operation is what they are designed for. Let the mixture settle before your first dose and route the output into a high-flow area of the sump.

What's Included

  • Kalk stirrer body with integrated stirring motor (15 W, 20 W or 25 W by model)
  • Power transformer (120 V to 24 V AC)
  • 1/4 in quick-connect input and output fittings
  • Internal stirrer arm and shaft

Recommended Pairings

FAQ

Does the reactor come with a pump?
No. Each model 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 motors are rated for about 1,500 hours of operation, so stir in short intervals on a timer or controller and let the unit rest between cycles.

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

Does this ship free?
No. The KS reactors are oversized packages, so they are excluded from our free shipping threshold and ship at the carrier rate shown at checkout. Local pickup at the store is always free.

Will kalkwasser cover all of my calcium and alkalinity demand?
Kalkwasser adds calcium and alkalinity in a balanced ratio and raises pH, which is enough for many mixed reefs. Tanks with very high demand may still need supplemental two-part dosing or a calcium reactor.

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Reef Octopus Nilson Kalk Reactor

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