Best CO2 Regulators and Accessories with a Setup Guide for Planted Tanks

Aquarium CO2 (carbon dioxide) is essential for aquatic plants during photosynthesis, enabling them to build new cells for growth. Most freshwater plants depend entirely on CO2 dissolved in water, unless they extend leaves above the surface to access atmospheric CO2. However, this dissolved CO2 is quickly depleted by plants and requires replenishment. A pressurized CO2 supply system offers the most convenient and effective solution for maintaining CO2 levels in a planted aquarium.

• How Does a Pressurized CO2 Supply System Work?
• Main CO2 Regulator Components and Accessories
  • Pressure Gauges
  • Solenoid Valve
  • Needle Valve
  • Bubble Counter
  • Diffuser (In-Tank or Inline)
  • CO2-Resistant Tubing
• [Comparison Table] CO2 Regulators for Planted Aquariums
• Best Planted Tank CO2 Regulator Reviews
  • FZONE Aquarium CO2 Regulator Mini-Series V3.0, Dual Stage
  • FZONE Aquarium CO2 Paintball Regulator, Single-Stage
  • FZONE Aquarium CO2 Regulator DC Solenoid Mini, Single Stage
  • FZONE Pro Series CO2 Regulator for Large Planted Tanks, Dual-Stage
  • Fluval Mini Pressurized CO2 Kit for Nano Planted Tanks
  • Basic AQUA TEK CO2 Regulator with Solenoid
• Other CO2 Accessories for Planted Aquariums
  • CO2 Cylinder Canisters
  • Timer for Solenoid Valve
  • Hydra Aquatic CO2 Paintball Adapter
  • CO2 Check Valve
  • Milwaukee Instruments 716690 pH Controller
• How Much CO2 for Planted Tanks?
• How to Measure CO2 in Planted Aquariums?
  • 1. Using pH, KH Test Kits, and a CO2 Chart
  • 2. Using a CO2 Drop Checker
• Does Your Tank Need a CO2 System?
• Frequently Asked Questions

How Does a Pressurized CO2 Supply System Work?

Pressurized CO2 Supply System

Understanding how a pressurized CO2 system operates may initially seem complex, especially for newcomers to planted aquariums. The system involves several components that might appear daunting at first. However, once you grasp their functions and purpose, it becomes clear and significantly boosts your success in growing aquatic plants.

The core of any pressurized CO2 system is a CO2 canister, where CO2 is stored under high pressure, converting it into a liquid at the canister’s base. To safely release this CO2 as a gas without causing damage, a CO2 regulator is essential.

The regulator reduces the pressure of the CO2 exiting the canister, transforming it back into a gaseous state for safe distribution.

CO2 Diffuser in a Planted Tank

This lower-pressure gas is then directed through CO2-rated airline tubing to a diffuser inside the aquarium. The diffuser breaks the CO2 into tiny micro-bubbles, which are readily absorbed by the water, aiding plant photosynthesis.

That covers the basics of a CO2 system. Additional equipment between the regulator and diffuser enhances efficiency and ensures optimal CO2 delivery to your planted aquarium.

Main CO2 Regulator Components and Accessories

You now know a pressurized CO2 canister and regulator are fundamental to safely extract CO2. This section breaks down the key components of a CO2 regulator and explains how to set it up to deliver the right amount of CO2 to your planted aquarium.

Pressure Gauges

The high-pressure gauge displays the CO2 pressure inside the canister, indicating the remaining CO2 level and signaling when a refill or replacement is needed. The low-pressure gauge (working pressure gauge) shows the adjusted output pressure after regulation.

Solenoid Valve

FZONE DC CO2 Solenoid Valve #ad

CO2 should only be injected when lights are on, as this is when plants photosynthesize. Manually adjusting the canister’s flow valve is possible but time-consuming and imprecise. A solenoid valve simplifies this process.

This magnetic device, when connected to a timer, controls CO2 flow—allowing it when powered on and stopping it when off. It automates CO2 delivery, saving time and resources.

Needle Valve

Needle Valve with Bubble Counter for regulator #ad

CO2 Needle Valve for tubing #ad

Needle Valve attachment

2 Way Splitter Regulator Valve #ad

Following the solenoid, the needle valve provides precise control (fine-tuning) of CO2 flow into the aquarium. While the regulator manages pressure, the needle valve adjusts the flow rate (bubbles per second).

Without it, excessive CO2 could oversaturate the water, harming aquarium inhabitants.

Bubble Counter

Rhinox Aluminum Alloy CO2 Bubble Counter #ad

Bubble counter for tubing #ad

To fine-tune the bubble rate, a bubble counter is invaluable. Some regulators include one that attaches post-solenoid.

Use a bubble counter

This glass tube, filled with water, lets you visually count CO2 bubbles. Adjust the needle valve to achieve the desired rate, starting at one bubble per second for a new planted tank.

Diffuser (In-Tank or Inline)

After pressure reduction and flow adjustment, CO2 passes through a diffuser, converting bubbles into micro-bubbles for better water absorption. Two main types exist, based on preference:

In-Tank Diffuser

Aquario Neo Co2 Diffuser, small #ad

JARDLI 2-inch Pollen Glass CO2 Diffuser for 50-80 Gal #ad

Similar to an air stone, these porous diffusers create a fine CO2 mist. Place them near the filter’s water return line to distribute CO2 evenly throughout the tank.

Inline Diffuser (CO2 Atomizer)

Aquarium Inline Co2 Atomizer Diffuser #ad

NilocG Aquatics Inline CO2 Atomizer Diffuser #ad

Favored for minimalist setups, inline diffusers attach to an external canister filter’s return line, injecting CO2 directly into the water flow.

CO2-Resistant Tubing

AQUATEK CO2-Proof Tubing 16 Feet, 3/16-inch inner diameter #ad

JARDLI CO2-Proof Tubing 16 Feet, 3/16-inch inner diameter #ad

High-quality CO2-resistant tubing is critical, as silicone tubing degrades under CO2 exposure, leading to leaks. This tubing connects the needle valve to the bubble counter and then to the diffuser.

[Comparison Table] CO2 Regulators for Planted Aquariums

Model	Our rating	Fitting	Output pressure	Solenoid	Other
	FZONE Aquarium CO2 Regulator Mini Series V3.0 #ad	CGA320, paintball, disposable cartridges	0 – 60 psi, adjustable	12V DC	needle valve, bubble counter, assembling tools
	FZONE Paintball Aquarium CO2 Regulator #ad	paintball	preset, not adjustable	12V DC	needle valve, bubble counter
	FZONE CGA320 Aquarium CO2 Regulator #ad	CGA320 thread	preset to 30-60 psi	12V DC (AC available)	needle valve, bubble counter, assembling tools
	FZONE Pro Series CO2 Regulator #ad	CGA320 thread	0 – 65 psi, adjustable	12V DC	two manifold blocks, needle valve, bubble counter, assembling tools
	Fluval Mini Pressurized CO2 Kit #ad	Fluval cartridge	nano planted tanks, < 15 gallons	not included	regulator valve, cartridge bracket, disposable CO2 cartridge, hose, and internal CO2 diffuser
	Basic AQUA TEK CO2 Regulator #ad	CGA320 thread	preset	included	bubble counter with integrated check valve, suction cup

Best Planted Tank CO2 Regulator Reviews

FZONE Aquarium CO2 Regulator Mini-Series V3.0, Dual Stage

• Check on Amazon #ad
• Fitting: CGA320 thread, paintball, disposable CO2 cartridges (5/8″ UNF)
• Output pressure: 0 – 60 psi, adjustable
• Solenoid: 12V DC
• Other: needle valve, bubble counter, assembling tools

The FZONE Mini-Series V3.0 offers versatile dual-stage control (pressure and needle valve), stabilizing output and preventing end-of-tank dumps (EoTD).

Multi-stage control #ad

Made from high-purity aluminum with a stainless-steel diaphragm, it’s durable and reliable.

FZONE Aquarium CO2 Regulator Mini Series V3.0 #ad

It includes an outflow gauge, pressure knob, 12V DC solenoid (0.4 watts, cool-running with an on/off indicator), a rotatable copper needle valve (adjustable to 0.3 bps), and a bubble counter with a check valve to prevent backflow.

Rotatable needle valve to fit on any style of CO2 tank #ad

The 360° rotatable needle valve accommodates any CO2 tank orientation. Compatible with CGA320, paintball, and 5/8″ UNF fittings (not Fluval cartridges), it suits various aquarium sizes.

FZONE Aquarium CO2 Paintball Regulator, Single-Stage

• Check on Amazon #ad
• Fitting: paintball
• Output pressure: preset, not adjustable
• Solenoid: 12V DC
• Other: needle valve, bubble counter

Designed exclusively for paintball CO2 tanks, this single-stage regulator features dual gauges for tank and outflow pressure (preset, non-adjustable).

Designed to fit paintball CO2 tanks #ad

It includes a 12V DC solenoid (0.4 watts, with on/off light), copper needle valve, and bubble counter with check valve. Constructed from aluminum and stainless steel, it’s built to last.

FZONE Aquarium CO2 Regulator DC Solenoid Mini, Single Stage

• Check on Amazon #ad
• Fitting: CGA320 thread
• Output pressure: preset to 30-60 psi
• Solenoid: 12V DC (AC option available)
• Other: needle valve, bubble counter, assembling tools

This single-stage regulator, designed for CGA320 North American CO2 canisters, features dual gauges with a preset 30-60 psi output.

Its 12V DC solenoid (2.5 watts, quiet and cool) connects to a timer (sold separately). Enhanced O-rings withstand -45°F to 90°F, with spares included. The copper needle valve and bubble counter allow precise adjustments down to 1 bubble per 5 seconds, with tools for easy setup.

FZONE Pro Series CO2 Regulator for Large Planted Tanks, Dual-Stage

• Check on Amazon #ad
• Fitting: CGA320 thread
• Output pressure: 0 – 65 psi, adjustable
• Solenoid: 12V DC
• Other: two manifold blocks, needle valve, bubble counter, assembling tools

Ideal for large CO2 setups, this dual-stage regulator prevents EoTD and features a safety valve releasing pressure above 100 psi.

FZONE Pro Series CO2 Regulator #ad

Dual gauges monitor tank and outflow pressure (adjustable 0-65 psi). The expandable manifold block supports multiple diffusers for large or multi-tank setups.

Expandable manifold block #ad

The copper needle valve adjusts to 0.3 bps, and bubble counters include check valves. The 12V DC solenoid (2.5 watts) pairs with timers, and it fits CGA320 tanks with included tools.

Fluval Mini Pressurized CO2 Kit for Nano Planted Tanks

• Check on Amazon #ad
• Fitting: Fluval disposable CO2 cartridge
• Ideal for: nano planted tanks, < 15 gallons
• Solenoid: not included
• Include: regulator valve, cartridge bracket, disposable CO2 cartridge, hose, and internal CO2 diffuser

Designed for nano tanks under 15 gallons, this kit includes a regulator with an adjustable flow knob for Fluval 20g cartridges, tubing, a bracket, and a ceramic diffuser. Lacking a solenoid, it’s not timer-compatible and includes one cartridge, with replacements available.

Basic AQUA TEK CO2 Regulator with Solenoid

• Check on Amazon #ad
• Fitting: CGA320 thread
• Output pressure: preset
• Solenoid: included
• Other: bubble counter with integrated check valve, suction cup

This straightforward brass regulator features dual gauges, a cool-touch solenoid, and a precision needle valve. Compatible with CGA320 fittings (paintball adapter not included), it includes an inline bubble counter with a check valve, suction cup, and clip for easy placement.

Other CO2 Accessories for Planted Aquariums

CO2 Cylinder Canisters

5lb CO2 Tank Aluminum Cylinder with CGA320 Valve #ad

Aluminum CO2 Paintball Tank #ad

The 5lb canister (CGA320, 1800 psi) and 20oz paintball canister require filling. Fluval mini cartridges are pre-filled and disposable, ideal for nano tanks if compatible with your regulator.

Timer for Solenoid Valve

BN-LINK 7 Day Heavy Duty Digital Programmable Timer #ad

This digital timer offers 7-day programming with 8 pre-sets for simultaneous light and CO2 control.

BN-LINK Compact Outdoor Mechanical Timer #ad

This waterproof mechanical timer provides 48 15-minute settings daily, with an always-on option.

Hydra Aquatic CO2 Paintball Adapter

Hydra Aquatic CO2 Paintball Adapter #ad

This adapter enables CGA320 regulators to use paintball tanks.

CO2 Check Valve

CO2 check valve #ad

Prevents backflow from damaging the regulator.

Milwaukee Instruments 716690 pH Controller

Milwaukee Instruments 716690 pH Controller #ad

For advanced users, this controller monitors pH accurately, triggering the solenoid to maintain a set range, bypassing drop checkers or test kits.

How Much CO2 for Planted Tanks?

CO2 levels affect dissolved oxygen, pH, and KH (carbonate hardness). A level of 30 ppm is optimal for plant growth and safe for most fish and invertebrates.

Toxicity depends on oxygen levels—low O2 increases CO2 sensitivity, while high O2 raises tolerance.

How to Measure CO2 in Planted Aquariums?

Dissolved CO2 forms carbonic acid, increasing KH and lowering pH. This relationship helps measure CO2 concentration:

H2O + CO2 <-> HCO3- (KH) + H+ (pH)

1. Using pH, KH Test Kits, and a CO2 Chart

Measure pH and KH daily with reagent kits, then reference a chart to estimate CO2. Add drops to aquarium water, match the color change to a chart, and calculate. Small misreadings (e.g., 0.2 pH or 0.5 KH) can skew CO2 dosing.

2. Using a CO2 Drop Checker

Drop checkers simplify monitoring with a fixed 4 dKH solution that changes color based on pH.

NilocG Aquatics Glass CO2 Drop Checker #ad

Placed visibly away from filter flow, it reflects CO2 levels: lime green (30 ppm), blue (20 ppm, too low), or yellow (40 ppm, risky). Adjust the needle valve accordingly.

Does Your Tank Need a CO2 System?

Fish produce some CO2 naturally, and many planted tanks thrive without added CO2. Test your setup first—if plants grow well, additional CO2 may be unnecessary. Aeration adds CO2 alongside O2, but excessive CO2 alters pH. For lush growth seen in magazines, a CO2 system might be ideal.

Frequently Asked Questions

Yes, API CO2 Booster provides an alternative to pressurized systems, releasing CO2 and organic carbon gradually for plant growth in fish tanks with plants.

How Does Supplying CO2 Help Control Algae?

With proper lighting, filtration, and nutrients, CO2 enhances photosynthesis, allowing plants to outcompete algae for resources.

How to Refill Aquarium CO2 Canisters?

Paintball tanks can be refilled at local stores, while larger 5lb or 10lb tanks require certified providers. Check canister compatibility.

How Long Does Aquarium CO2 Last?

A 5lb tank with a solenoid and timer lasts 5 weeks to 3 months, depending on tank size and CO2 demand.

Aquarium With and Without CO2?

Without injection, residual CO2 from decomposition exists, but high-light, heavily planted tanks need supplemental CO2 for success.

How Do Aquarium Carpet Plants Do Without CO2?

In high light with low CO2, carpet plants struggle. Lower light, quality soil, fertilizers, and surface agitation can support growth.

How Many Bubbles Per Second of CO2?

Start at 1 bps, adjusting with a drop checker to reach optimal CO2 levels.

How Many Hours Do You Inject CO2?

Inject CO2 only when lights are on, typically 8-12 hours, tailored to plant needs with daily tweaks.