Till today many may still not know how to determine your co2 level in your aquarium. Whether is the co2 sufficient or insufficient. Whether a high-tech tank with co2 cylinder or a low-tech D.I.Y yeast co2 mixture. It is always better to have something that you could judge and know the condition of your aquarium.
Below is a CO2 Checker which there are varieties of co2 checker brands as well. I picked the one simply just for demonstration purposes only.
If you are wondering how much CO2 Bubble Per Second(BPS) need for your aquarium, I couldn’t answer you that as every aquarium may be vary and depends on the amount of plants and the demand of the plants as well.A recommended co2 bps is around 3, where higher demand plants require about 4-8. This is a very subjective matter, so it is advisable for you to do a try and error for your co2 setup.
If you require super high co2 bps but your fish is already gasping for air,
providing extra O2 Oxygen is your alternate way to keep the fish happy and still cranking up for more co2 into your aquarium.