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CO₂

Drop checker + 4dKH ref

co2

Used for: Planted tanks, CO2 injection

Specifications

NilocG Aquatics Glass CO2 Drop Checker – CO2 Monitor Kit for Aquarium Tank – Functional and Reliable – Transparent Drop Checker, 4dkh/pH Reagent Solution and Suction Cup
Specification	Value
Material	glass
Supplied reagent	60ml bottle of 4dkh/pH reagent solution

Source checked on 2026-10-02.

Pawfly Glass CO2 Drop Checker for Aquarium CO2 Indicator for Planted Fish Tank CO2 Monitor Kit with Solution & Suction Cups CO2 Detector Aquarium CO2 Tester Fish Tank Carbon Dioxide Checker
Specification	Value
Material	glass
Supplied reagent	2 bottles of reagent solution

Source checked on 2026-10-02.

Description

A drop checker holds indicator liquid in a glass vessel to provide a visual indication of aquarium CO2 conditions. Use the solution and mounting method intended for the checker, keeping the indicator separated from tank water by the designed air space. Choose a complete kit or a replacement checker according to what you need. The NilocG kit includes a glass checker and a 60 ml bottle of 4 dKH/pH reagent. The Pawfly two-piece kit includes glass checkers and two reagent bottles; their dKH concentration is unspecified. Use each kit’s matching solution and colour guide. Allow for the reaction delay when changing gas delivery. The NilocG and Pawfly kits specify about two hours for a reading, while Dennerle’s long-term indicator guidance allows two to three hours after a change. A drop checker provides delayed visual feedback; it does not directly control a solenoid.

Sources

Further reading on identification and aquarium care.

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