The Co2 Drop Checker How To Help Guide - Aquarium Gardens

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Home > Plant Care The CO2 Drop Checker

Monitoring and maintaining the correct CO2 levels in your planted aquarium is vital. The drop checker is a reservoir for an indicative fluid that tells you whether you have too much, too little or the correct levels of CO2 for your plants to grow, and that is a safe level for fish. How to install your CO2 Drop Checker

1. Invert your drop checker and fill the reservoir up half way with CO2 drop checker indicator solution.
2. Using the suction cup, submerge the drop checker into your aquarium water and stick to the aquarium glass sides.
3. Based on the concentration of your CO2 in your water, the colour of the solution will change.
4. Check the colour. Blue = too little CO2 concentration, Yellow = too much CO2 (dangerous levels for fish), Green = optimum levels for plants and fish. The colour has a 1-2 hour delay. So what you are reading is the CO2 concentration roughly 1-2 hours ago.
5. Based on your reading, adjust your CO2 bubble rate using your regulator if required. Wait a further 2 hours for concentration of CO2 to change and check your readings.

Too Little CO2

Too Much CO2

Correct Levels of CO2

As a guide, usually between 1 - 3 bubbles per second through your bubble counter is usually enough to get a green reading on tanks up to 200 L. Adjust this according to your tank size and what your drop checker is indicating. If you are having problems getting a reading then you have not diffused enough CO2 into your water. Try adjusting/increasing your circulation or re-positioning your diffuser towards the direction of flow to aid diffusion rates. Alternatively, positioning your diffuser near your filter inlet will allow the bubbles to travel through your filter, increasing the effectiveness of your CO2 diffusion. The aim is to keep the bubbles in your water for as long as possible to increase the effectiveness of CO2 diffusion in your aquarium water. Make small adjustments until you get a green reading on your drop checker. Be careful not to go overboard and gas your fish. VAT Number: 202531463 © Copyright 2025 Aquarium Gardens All rights reserved

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