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CO2 (Carbon Dioxide) is useful both in freshwater and marine environments. 
In the freshwater aquarium, CO2 enhances your ability to successfully keep live aquatic plants.  As green plants photosynthesize, they utilize carbon dioxide. Without CO2, live aquarium plants will have a hard time thriving in the closed aquarium system.
In the marine aquarium, CO2 is used to lower the pH of calcium reactor effluent in order to dissolve hydrocarbonate media into bio-available calcium molecules. Calcium is then utilized by corals and other marine organisms mainly for skeleton building.

At AquaCave, we offer some of the best selection and best prices on CO2 accessories including CO2 regulators, CO2 Tanks, CO2 solenoid valves, pH controllers, CO2 reactors, CO2 diffusers and needle valves for your marine, reef, and freshwater aquarium.

60 of 82 Items
  • CarbonDoser Electronic CO2 Regulator V2

    CarbonDoser

    CarbonDoser Electronic CO2 Regulator V2

    CarbonDoser Electronic CO2 Regulator V2 The new V2.0 allows for the aquarist to position the CO2 cylinder out of the way in a remote area. Then mounting the "box" anywhere such as up on a board with all the electronics/pH controllers/ETC The 1/8"...

    $439.99
  • CarbonDoser Controller

    CarbonDoser

    CarbonDoser Controller

    CarbonDoser Controller For a targeted and very precise CO2 supply in freshwater aquariums, or into calcium reactors. Features an electronically controlled valve that produces one CO2 portion / CO2 bubble every 0.1 to 10 seconds. The number of bubbles /...

    $349.99
  • Fluval BIO CO2 500L Fluval BIO CO2 500L Fluval BIO CO2 500L Fluval BIO CO2 500L Fluval BIO CO2 500L

    Fluval

    Fluval BIO CO2 500L

    Fluval BIO CO2 500L The Bio-CO2 Pro system combines the safety of biological carbon dioxide production with the convenience of pressurized delivery. Offering simplicity and unparalleled performance in an easy-to-use format, Bio-CO2 delivers reliable and...

    $349.99
  • Deluxe Calcium Reactor Package

    AquaCave

    Deluxe Calcium Reactor Package

    Deluxe Calcium Reactor Package Turn your calcium reactor into a complete automated unit by adding our Deluxe CO2 Package.Can be used with any calcium reactor on the market. It includes everything you'll need to setup and automate your calcium dosing...

    $349.95
  • Deluxe Planted Tank CO2 Package

    AquaCave

    Deluxe Planted Tank CO2 Package

    Deluxe Planted Tank CO2 Package Our Deluxe Planted Tank CO2 Package includes everything you'll need to setup and automate your CO2 dosing. Package Includes: - Your Choice of CO2 Cylinder - Your Choice of CO2 Regulator with solenoid valve -...

    $329.95
  • Eheim CO2 Regulator Set 600 Eheim CO2 Regulator Set 600

    Eheim

    Eheim CO2 Regulator Set 600

    Eheim CO2 Regulator Set 600 EHEIM CO²Set600 without bottle Aquarium water usually contains too little carbon dioxide (CO2) as it has already been extracted from the tap water at the waterworks. In addition to light, nitrogen, phosphate and trace...

    $249.99
  • Milwaukee MC125 PRO 2-in-1 Digital pH/ORP Controller Milwaukee MC125 PRO 2-in-1 Digital pH/ORP Controller Milwaukee MC125 PRO 2-in-1 Digital pH/ORP Controller Milwaukee MC125 PRO 2-in-1 Digital pH/ORP Controller

    Milwaukee Instruments

    Milwaukee MC125 PRO 2-in-1 Digital pH/ORP Controller

    Milwaukee MC125 PRO 2-in-1 Digital pH/ORP Controller DESCRIPTION The Milwaukee MC125 PRO pH and ORP controller is designed for people looking to measure and adjust pH and ORP levels automatically with one simple controller. Just set your pH and ORP ...

    $229.90
  • 20 lb. Aluminum CO2 Cylinder

    AquaCave

    20 lb. Aluminum CO2 Cylinder

    20 lb. Aluminum CO2 Cylinder, New. 28" tall with valve. 8" in Diameter. CO2 Cylinders are shipped empty. Check your phone book under Fire Extinguishers, Fire and Safety Equipment or Welding Gas & Equipment for local companies where you will be able...

    $199.99
  •  Pinpoint pH Controller    Pinpoint pH Controller

    Pinpoint - American Marine

    Pinpoint pH Controller

    Pinpoint pH Controller by American Marine PINPOINT pH Controller™ is an inexpensive yet rugged controller, which includes the appropriate probe and calibration fluids. This device will automate another electrical device such as a calcium reactor or...

    $199.95
  • Fluval BIO CO2 250L Fluval BIO CO2 250L

    Fluval

    Fluval BIO CO2 250L

    Fluval BIO CO2 250L The Fluval Bio CO2 Pro System 250L is a high-quality CO2 system designed for aquariums with a capacity of up to 250 liters. This system, manufactured by Fluval, helps to provide essential carbon dioxide to aquatic plants, promoting...

    $174.99
  • 10 lb. Aluminum CO2 Cylinder

    AquaCave

    10 lb. Aluminum CO2 Cylinder

    10 lb. Aluminum CO2 Cylinder, New. 22" tall with valve. 6.9" in Diameter. CO2 Cylinders are shipped empty. Check your phone book under Fire Extinguishers, Fire and Safety Equipment or Welding Gas & Equipment for local companies where you will be...

    $159.99
  • SR Aquaristik Aquarium Single Stage CO2 Regulator Kit SR Aquaristik Aquarium Single Stage CO2 Regulator Kit SR Aquaristik Aquarium Single Stage CO2 Regulator Kit SR Aquaristik Aquarium Single Stage CO2 Regulator Kit SR Aquaristik Aquarium Single Stage CO2 Regulator Kit

    SR Aquaristik

    SR Aquaristik Aquarium Single Stage CO2 Regulator Kit

    SR Aquaristik Aquarium Single Stage CO2 Regulator Kit For Aquarium Plants Calcium Reactors Ideal for planted aquariums and calcium reactors Precise control of CO2 output Displays canister pressure & CO2 output Compatible with most ph...

    $159.95
  • YCA Dual CO2 Regulator with Solenoid Valve YCA Dual CO2 Regulator with Solenoid Valve YCA Dual CO2 Regulator with Solenoid Valve

    Your Choice Aquatic

    YCA Dual CO2 Regulator with Solenoid Valve

    YCA Dual CO2 Regulator with Solenoid Valve Dual Stage CO2 Regulator contains two gauges to show both working pressure and gas pressure in your tank.  Package Includes: Dual Stage CO2 Regulator 2x Bubble Counter Select Tools Power...

    $149.99
  • Milwaukee MC122 pH Controller Milwaukee MC122 pH Controller Milwaukee MC122 pH Controller Milwaukee MC122 pH Controller Milwaukee MC122 pH Controller

    Milwaukee Instruments

    Milwaukee MC122 pH Controller

    Milwaukee MC122 pH Controller. ACCURATE. SIMPLE. RELIABLE. 24/7 PH CONTROL. The Milwaukee MC122 PRO pH controller lets you measure and adjust pH levels automatically. WHAT PEOPLE ARE SAYING "I run this unit 24/7 and have not had any problems for the...

    $147.40
  • American Marine Pinpoint CO2 Regulator

    Pinpoint - American Marine

    American Marine Pinpoint CO2 Regulator

    American Marine Pinpoint CO2 Regulator.The PINPOINT¨ CO2 Regulator Kit is now available. This is a high end regulator/solenoid engineered specifically for the aquarium hobby at an affordable price. The PINPOINT¨ CO2 Regulator Kit comes complete:*...

    $139.95
  • Fluval BIO CO2 125L Fluval BIO CO2 125L

    Fluval

    Fluval BIO CO2 125L

    Fluval BIO CO2 125L The Fluval Bio Co2 Pro System 125L is a high-quality CO2 system designed for aquariums with a capacity of 125 liters. This system, manufactured by Fluval, helps to promote healthy plant growth in your aquarium by providing a steady...

    $138.99
  • Tunze CO2 Regulator, 7077/3 Tunze CO2 Regulator, 7077/3 Tunze CO2 Regulator, 7077/3 Tunze CO2 Regulator, 7077/3

    Tunze

    Tunze CO2 Regulator, 7077/3

    Tunze CO2 Regulator, 7077/3. Precision device with fine adjustment for standard CO2 cylinders, thread in keeping with German standard DIN 477 (US version with CGA 320 thread). To be mounted without tools; precise adjustment; two pressure gauges;...

    $129.99
  • Milwaukee CO2 Regulator w/Solenoid Valve, MA957

    Milwaukee Instruments

    Milwaukee CO2 Regulator w/Solenoid Valve, MA957

    Milwaukee CO2 Regulator w/Solenoid Valve, MA957. CO2 regulator by Milwaukee Instruments includes solenoid valve and bubble counter. Unit comes with dual gauges each with dual reading of both psi & kg/cm. Left gauge meters tank capacity and right...

    $115.50
  • 5 lb. Aluminum CO2 Cylinder

    AquaCave

    5 lb. Aluminum CO2 Cylinder

    5 lb. Aluminum CO2 Cylinder, New. 19" tall with valve. CO2 Cylinders are shipped empty. Check your phone book under Fire Extinguishers, Fire and Safety Equipment or Welding Gas & Equipment for local companies where you will be able to refill the CO2...

    $99.99
  • Milwaukee CO2 Solenoid Valve, MA955 Milwaukee CO2 Solenoid Valve, MA955 Milwaukee CO2 Solenoid Valve, MA955

    Milwaukee Instruments

    Milwaukee CO2 Solenoid Valve, MA955

    Milwaukee Brass Solenoid Valve comes with a 6 foot power cord. 1/8 inch FPT input and output. 3 WattsMilwaukee Brass Solenoid Valve comes with a 6 foot power cord. 1/8 inch FPT input and output. 3 WattsProduct code: 127Item No. CO-MA955

    $67.00
  • 6 Way Co2 Manifold 6 Way Co2 Manifold

    AquaCave

    6 Way Co2 Manifold

     6 Way Co2 Manifold Description: Made from high grade aluminum alloy and stainless steel, the solid constructions ensure long-lasting durability and dependability.With this splitter, you can easily connect up to three or two CO2 diffusers/supplies...

    $59.95
  • Sera Flore Active CO2 Reactor 500 - 66-160 Gal. Sera Flore Active CO2 Reactor 500 - 66-160 Gal.

    Sera

    Sera Flore Active CO2 Reactor 500 - 66-160 Gal.

    Sera Flore Active CO2 Reactor 500 - Small 66-160 Gal The new sera flore CO2 active reactors 500 and 1000 with twin rotor supersede the generation of static CO2 generators. The rotors, the upper one of which is designed as a lamella rotor,...

    $59.95
  • 5 Way Co2 Manifold 5 Way Co2 Manifold

    AquaCave

    5 Way Co2 Manifold

     5 Way Co2 Manifold Description: Made from high grade aluminum alloy and stainless steel, the solid constructions ensure long-lasting durability and dependability.With this splitter, you can easily connect up to three or two CO2 diffusers/supplies...

    $54.95
  • 4 Way Co2 Manifold 4 Way Co2 Manifold

    AquaCave

    4 Way Co2 Manifold

     4 Way Co2 Manifold Description: Made from high grade aluminum alloy and stainless steel, the solid constructions ensure long-lasting durability and dependability.With this splitter, you can easily connect up to three or two CO2 diffusers/supplies...

    $49.95
  • CO2 Turbo Diffuser 600 CO2 Turbo Diffuser 600 CO2 Turbo Diffuser 600 CO2 Turbo Diffuser 600

    Mr. Aqua

    CO2 Turbo Diffuser 600

    CO2 Turbo Diffuser 600 Mr. Aqua’s CO2 Turbo Diffuser has a patented power scatter design that provides a fast, effective way to diffuse carbon dioxide into the water for plants. The powerhead driven atomizer and patented multilayer compression...

    $49.95
  • 3 Way Co2 Manifold 3 Way Co2 Manifold

    AquaCave

    3 Way Co2 Manifold

     3 Way Co2 Manifold Description: Made from high grade aluminum alloy and stainless steel, the solid constructions ensure long-lasting durability and dependability.With this splitter, you can easily connect up to three or two CO2 diffusers/supplies...

    $44.95
  • CO2 Turbo Diffuser 400 CO2 Turbo Diffuser 400 CO2 Turbo Diffuser 400 CO2 Turbo Diffuser 400

    Mr. Aqua

    CO2 Turbo Diffuser 400

    CO2 Turbo Diffuser 400 Mr. Aqua’s CO2 Turbo Diffuser has a patented power scatter design that provides a fast, effective way to diffuse carbon dioxide into the water for plants. The powerhead driven atomizer and patented multilayer compression...

    $44.95
  • Sera CO2 Start Kit

    Sera

    Sera CO2 Start Kit

    Sera CO2 Start Kit. **** PRODUCT MANUAL **** Carbon dioxide (CO2) is the basic nutrient for plants. A well-dosed addition of CO2 also allows you to adjust the water to a slightly acidic pH range, which is preferred by most plants and fish kept in...

    $39.99
  • 2 Way Co2 Manifold 2 Way Co2 Manifold

    AquaCave

    2 Way CO2 Manifold

     2 Way Co2 Manifold Description: Made from high grade aluminum alloy and stainless steel, the solid constructions ensure long-lasting durability and dependability.With this splitter, you can easily connect up to three or two CO2 diffusers/supplies...

    $39.95
  • CO2 Turbo Diffuser 200 CO2 Turbo Diffuser 200 CO2 Turbo Diffuser 200

    Mr. Aqua

    CO2 Turbo Diffuser 200

    CO2 Turbo Diffuser 200 Mr. Aqua’s CO2 Turbo Diffuser has a patented power scatter design that provides a fast, effective way to diffuse carbon dioxide into the water for plants. The powerhead driven atomizer and patented multilayer compression...

    $39.95
  • Replacement CO2 Cartridges, 3 PACK for Pierce CO2 System

    Azoo

    Replacement CO2 Cartridges, 3 PACK for Pierce CO2 System

    Replacement CO2 Cartridges,3 PACK, for Pierce CO2 System. For larger planted aquariums we recomend aquiring the multi pack replacement cartridges for the multi pack allows for having extra bottles on hand to prevent running out and creating ph swings as...

    $39.95
  • Up Aqua Co2 Inline Diffuser 1/2" Up Aqua Co2 Inline Diffuser 1/2" Up Aqua Co2 Inline Diffuser 1/2" Up Aqua Co2 Inline Diffuser 1/2"

    Up Aqua

    Up Aqua Co2 Inline Diffuser 1/2"

    Up Aqua Co2 Inline Diffuser 1/2" Description: Co2 In-line Atomizers. Works with higher pressure than standard glass diffusers. Hooks up in-line to canister filter. Co2 is diffused trough fine ceramic atomizer tube. Atomized Co2 than travels trough...

    $39.95
  • Up Aqua Co2 Inline Diffuser 5/8" Up Aqua Co2 Inline Diffuser 5/8" Up Aqua Co2 Inline Diffuser 5/8"

    Up Aqua

    Up Aqua Co2 Inline Diffuser 5/8"

    Up Aqua Co2 Inline Diffuser 5/8" Description: Co2 In-line Atomizers. Works with higher pressure than standard glass diffusers. Hooks up in-line to canister filter. Co2 is diffused trough fine ceramic atomizer tube. Atomized Co2 than travels trough...

    $39.95
  • CarbonDoser CO2 Precision Check Valve CarbonDoser CO2 Precision Check Valve CarbonDoser CO2 Precision Check Valve CarbonDoser CO2 Precision Check Valve

    CarbonDoser

    CarbonDoser CO2 Precision Check Valve

    CarbonDoser® Precision Check Valve "Corrosion Resistant" (4 psi CRP) After years of experience with CO2 systems, we discovered why consistent "bubble counts" are, most of the time, impossible. Here's why: ALL checkvalves, even...

    $29.99
  • CarbonDoser Power Supply CarbonDoser Power Supply

    CarbonDoser

    CarbonDoser Power Supply

    CarbonDoser Power Supply CarbonDoser Electronic Power Supply (U.S.A.)replacement power supply for: CarbonDoser Electronic CO2 Regulator (does not fit the original "AquariumPlants.com's own" regulator)  CarbonDoser Electronic Power Supply (U.S.A...

    $29.99
  • HYDROS DC CO2 Solenoid Valve HYDROS DC CO2 Solenoid Valve HYDROS DC CO2 Solenoid Valve

    HYDROS

    HYDROS DC CO2 Solenoid Valve

    HYDROS DC CO2 Solenoid Valve The HYDROS DC CO2 Solenoid Valve is electronically controlled and plugs into a Drive Port on the Control 2 and Control 4 where it can be monitored and controlled via the HYDROS app.  The HYDROS DC CO2 Solenoid...

    $29.99
  • SR Aquaristik CO2 Regulator Expansion Module SR Aquaristik CO2 Regulator Expansion Module SR Aquaristik CO2 Regulator Expansion Module SR Aquaristik CO2 Regulator Expansion Module SR Aquaristik CO2 Regulator Expansion Module

    SR Aquaristik

    SR Aquaristik CO2 Regulator Expansion Module

    SR Aquaristik CO2 Regulator Expansion Module The SR Aquaristik CO2 Expansion Module is ideal for hobbyists who want to run more than one aquarium with one regulator. This simple to install independent control makes it quick and easy to expand your new...

    $29.98
  • Dennerle High Quality CO2 Check Valve Dennerle High Quality CO2 Check Valve

    Dennerle

    Dennerle High Quality CO2 Check Valve

    Dennerle High Quality CO2 Check Valve A very high-quality German CO2 check valve for freshwater or marine applications. A middle level priced and quality check valve between the Metallic and the Plastic ones. Takes 4/6 mm (ID/OD) or 1/8" airline tubing...

    $26.99
  • DIY CO2 Generator Kit DIY CO2 Generator Kit DIY CO2 Generator Kit DIY CO2 Generator Kit DIY CO2 Generator Kit

    AquaCave

    DIY CO2 Generator Kit

    DIY CO2 Generator Kit CO2 Generator: AS an indispensable role in the photosynthesis of aquatic plants, this CO2 aquarium kit for co2 diffuser for aquarium plants main for provides a genuine environment for plants' growing in aquarium and well provide...

    $19.99
  • Fluval BIO CO2 250 Diffuser Fluval BIO CO2 250 Diffuser Fluval BIO CO2 250 Diffuser

    Fluval

    Fluval BIO CO2 250 Diffuser

    Fluval BIO CO2 250 Diffuser Features Made of a clear, durable acrylic High-quality ceramic disc creates an ultra-fine mist for optimized solubility and plant absorption Available in 3 sizes to suit most aquariums What’s...

    $19.99
  • Fluval BIO CO2 125 Diffuser Fluval BIO CO2 125 Diffuser Fluval BIO CO2 125 Diffuser

    Fluval

    Fluval BIO CO2 125 Diffuser

    Fluval BIO CO2 125 Diffuser Features Made of a clear, durable acrylic High-quality ceramic disc creates an ultra-fine mist for optimized solubility and plant absorption Available in 3 sizes to suit most aquariums   What’s...

    $17.99
  • Co2 Needle Valve - NV-1 Co2 Needle Valve - NV-1 Co2 Needle Valve - NV-1

    AquaCave

    Co2 Needle Valve - NV-1

    Co2 Needle Valve - NV-1 Brand New & High Quality. Precise structure, durable stainless steel inner part with aluminum alloy to release CO2 by fine tuning. Special metal-grinded surface, light weight, easy to operate. Ergonomically design, easy...

    $17.95
  • Fluval CO2 Indicator Set Fluval CO2 Indicator Set

    Fluval

    Fluval CO2 Indicator Set

    Fluval CO2 Indicator Set The Fluval CO2 Indicator set is used to monitor approximate CO2 levels and also helps gauge CO2 levels in aquariums. The kit includes : CO2 Indicator 10 mL (0.34 fl oz) CO2 Indicator Solution Color reference sticker to...

    $17.95
  • Co2 Bubble Counter - MBC-1 Co2 Bubble Counter - MBC-1

    AquaCave

    Co2 Bubble Counter - MBC-1

    Co2 Bubble Counter - MBC-1 Glass made, nice and beautiful. High bending resistance, refining effect is good. For prevented water from flowing back into solenoid and the cylinder. With the use of the water table, can be...

    $14.95
  • CO2 Glass Diffuser, MA-003

    Azoo

    CO2 Glass Diffuser, MA-003

    CO2 Glass Diffuser, MA-003Specifications:- Made with fine ceramic, to dispense CO2 in mist form..CO2 Glass Diffuser, MA-003.Specifications:- Made with fine ceramic, to dispense CO2 in mist form.- Compact design, durable construction.- 2 suction cups...

    $14.95
  • CO2 Glass Diffuser, MA-004

    Azoo

    CO2 Glass Diffuser, MA-004

    Glass Blown Glass Diffuser, MA-004. Specifications: - Made with fine ceramic, to dispense CO2 in mist form - Compact design, durable construction - 2 suction cups included - Can be cleaned Instructions: When installing pressure pipes from the CO2...

    $14.95
  • SR Aquaristik In-Line CO2 Bubble Counter SR Aquaristik In-Line CO2 Bubble Counter SR Aquaristik In-Line CO2 Bubble Counter SR Aquaristik In-Line CO2 Bubble Counter

    SR Aquaristik

    SR Aquaristik In-Line CO2 Bubble Counter

    SR Aquaristik In-Line CO2 Bubble Counter Helps protect solenoid valve or regulator from backflow Can be used with water or glycerin to count the quantity of CO2 Easy to setup and use Fits on standard CO2 hose The SR Aquaristik inline CO2 bubble...

    $14.95
60 of 82 Items