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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.

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  • 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...

    Was: $506.53
    Now: $481.20
  • 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 -...

    Was: $485.53
    Now: $461.25
  • 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"...

    $449.99
  • 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...

    $208.15
  • 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
  • Milwaukee CO2 Regulator w/Solenoid Valve, MA957 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...

    $156.75
  • 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 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

    $94.88
  • 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...

    $59.99
  • 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...

    $54.99
  • 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
  • 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
  • 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
  • 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
  • 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
  • CO2 Glass Diffuser, MA-002

    Azoo

    CO2 Glass Diffuser, MA-002

    CO2 Glass Diffuser, MA-002Specifications:- Use to count Co2 bubble dispense in planted aquarium- Compact design, durable construction.- 2 suction cups included- Can be cleaned.Instructions:When installing pressure pipes from the CO2 regulator, the pipe...

    $11.95
  • CO2 Check Valve, Stainless Steel, IA-962

    Azoo

    CO2 Check Valve, Stainless Steel, IA-962

    CO2 Check Valve, Stainless Steel, IA-962. The check valve is usually placed between the CO2 regulator and the bubble to prevent water from back-flowing to the regulator.Fits standard 1/4" OD tubing.CO2 Check Valve, Stainless Steel, IA-962. The check...

    $9.95
  • Seachem CO2 Indicator Solution 50ml Seachem CO2 Indicator Solution 50ml

    Seachem

    Seachem CO2 Indicator Solution 50ml

    Seachem CO2 Indicator Solution 50ml CO2 Indicator Solution is for use with the Seachem glass pH Checker. This indicator solution changes color according to changes in the pH of the aquarium as a result of CO2 gas. The pH checker makes monitoring CO2...

    $7.99
  • Bubble Counter Liquid 50ml.

    Bubble Counter Liquid 50ml.

    Bubble Counter Liquid 50ml. Special high viscosity liquid to prevent evaporation and spillage in Bubble Counter. To be used externally only and comes in 50 mL spout cap for easy & direct application.  Imported from Germany.Bubble Counter...

    $7.95
  • Azoo CO2 Check Valve

    Azoo

    Azoo CO2 Check Valve

    Azoo CO2 Check Valve Plastic check valve for water plant aquariums. The check valve is usually placed between the CO2 regulator and the bubble to prevent water from back-flowing to the regulator.Azoo CO2 Check Valve Plastic check valve for water plant...

    $6.95
  • CO2 Tubing 1/4" O.D. per foot

    Milwaukee Instruments

    CO2 Tubing 1/4" O.D. per foot

    Regular air tubing can lose up to 25% of its CO2 before it even enters the tank. Sillicon tubing loses up to 5%. This unique CO2 resistant tubing loses less than 1%. Regular air tubing can lose up to 25% of its CO2 before it even enters the tank...

    $0.79
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