My drop checker won’t change from blue – is it working?

Sure is and its giving you a clear message too.

If your drop checker is staying blue, there is almost zero CO2 in your water. But here’s the thing…

Drop checkers don’t actually monitor CO2, they monitor pH. When you add CO2 (an acidic gas) into your tank, it reduces the pH. When your drop checker is showing blue, it’s telling you the pH is around 8 (far too high for plants). As you inject CO2 your drop checker will change colour (assuming you’re injecting enough CO2). The solution will begin to look a bit more green. When it hits a nice shade of green it means your pH is about 6.8 and your CO2 levels are 30ppm (parts per million). Green is the ideal colour to aim for and what you need to strive for.

But all too often hobbyists don’t inject ANYWHERE ENOUGH CO2. In a 100L tank, you need to start with 1 bubble per second for 8 hours a day.

Any changes you make to your CO2 flow rate needs to be done slowly. Remember your drop checker operates in the past – it’s not like a test kit in the respect that you take a sample of water and do a reading. There’s a delay of about 2 hours – this is how long it takes for your drop checker to change colour. So if you tweak your CO2 levels now, wait 2 hours, then see what colour it has changed to.

Always make small gradual changes to CO2 flow rate, otherwise you could overdose your fish with CO2 and see them gasping at the surface of your tank.

Make sense? Any questions?

4 thoughts on “My drop checker won’t change from blue – is it working?”

  1. I’m using an all new ADA set up which includes the drop checker. I’m using CO2 and it’s a nice green colour. I’ve read that you should use a solenoid valve for night time. Is this really necessary? Can you overload your plants with CO2? I imagined nature doesn’t switch off it’s CO2 supply to plants at night so why do we?

    1. Yes it’s necessary. Not only does it save CO2 but it stops your fish from being gassed to death. When lights are off, CO2 should be off.

      In nature, it’s very different as the amount of water you are dealing with is so huge.

    2. The simple answer is that nature also doesn’t exist in an artificial glass box, with artificial lighting and no constant flow of fresh water entering and waste water leaving. Co2 is used when lights are on only, or daylight a little for photosynthesis. What do you think happens at night when theres’s no uptake of it or light, and nowhere for the gas to go but in the water?

  2. Newbie with aquascapes, years with tropical livebearer fish. My last tank sprung a leak after having it set up and healthy for over 20 years. Even had a few hatchet tetras that lived for 12 years in the tank. With my new tank, I decided to try aquascaping. I have a 20 high tank with pressurized co2 regulated bubble counter at the electric solenoid controlled pressure regulator. I have over the past two months tried two times to place a black molly in the tank. They actually went hyper for a few moments after a day or so before they went to the rear of the tank and expired. I have a drop checker for the co2 levels and it never gets green but stays at blue. I have had it set up now for about 3 months. Since the checker uses a PH solution to check co2 levels in the air above the solution is it possible that the driftwood might be messing with the PH enough to prevent the solution in the drop checker from changing? The water has been checked by the local shop where I buy fish. They say it is perfect but resonably they cannot check co2.

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