Confusion on usage of drop checker

[argnom]

Hi everybody,

I'm a little confused... and this is the best place to turn for help.

I recently purchased a CO2 drop checker from Redsea. It seems to work well enough, but unfortunately I'm not certain that I'm getting an "accurate" result (well as accurate as possible with a cheap test anyway).

When I look at articles about DYI drop checkers, it is often mentionned to use a 4 dkh buffered solution + somekind of standard PH reagent solution.

The manual that came the Redsea's product mentions that I should use 1ml of water from my tank + 2 drops of their PH reagent.

Maybe I'm splitting hairs here. The drop checker is basically a PH test, but since PH can be affected by both the quanties of dissolved CO2 and the KH of the water, the only way to get an accurate result should be to use a buffered solution. Right?

/This could explain why the people wirtting the manual "forgot" to indicate blue=x ppm, green=y ppm and yellow=z ppm.
//I guess than mentionning that "You need to make your own buffered solution for it to work properly... suckers" is not good marketing...

 

[rodrigaj]

Hi everybody,

I'm a little confused... and this is the best place to turn for help.

I recently purchased a CO2 drop checker from Redsea. It seems to work well enough, but unfortunately I'm not certain that I'm getting an "accurate" result (well as accurate as possible with a cheap test anyway).

When I look at articles about DYI drop checkers, it is often mentionned to use a 4 dkh buffered solution + somekind of standard PH reagent solution.

The manual that came the Redsea's product mentions that I should use 1ml of water from my tank + 2 drops of their PH reagent.

Maybe I'm splitting hairs here. The drop checker is basically a PH test, but since PH can be affected by both the quanties of dissolved CO2 and the KH of the water, the only way to get an accurate result should be to use a buffered solution. Right?
/This could explain why the people wirtting the manual "forgot" to indicate blue=x ppm, green=y ppm and yellow=z ppm.
//I guess than mentionning that "You need to make your own buffered solution for it to work properly... suckers" is not good marketing...

Right. The indicator (bromothymol blue), when used with a 4dkh will give a gross indication of CO2 level. Forget about trying to extrapolate exact ppm measurements from it.

FWIW, it's not very useful even with a 4dkh solution because CO2 dispersement in a tank can vary so much depending on flow rates throughout the tank.

Its better to monitor the progess of plant growth and fish stress. If your plants are doing great and your fish are not gasping on top 5 hours after lights out your're ok.

Good flow is best determined by plant movement.

If you want ppm (I went through that phase once ) you will need a dKH test kit and a decent pH test kit. Phenol red with a pH range of 6.5 - 8.5 provides the level of precision that you need. I'm assuming that you have seen the dKH, pH, CO2 tables.

 

[VaughnH]

There is only one way I'm aware of for accurately measuring the amount of dissolved CO2 in water, and that is by use of a $2000 piece of test equipment, such as Tom has. I know for sure that measuring the KH and pH of the tank water will not tell you how much CO2 is in the water, unless you are sure your water has nothing in it that affects either pH or alkalinity other than carbonates and CO2. None of us have that.

Before the drop checker, many of us relied on the KH/pH measurement to see how much CO2 we had. When we did that we very often found that we had 60+ ppm of CO2, enough to kill most fish, but the fish were all very happy. Some of us even found that we had 100+ ppm of CO2, with happy fish. But, to be safe, we would drop the bubble rate until we had a nice, safe 20 ppm. And, we also had BBA all over the tank.

With the drop checker, used with distilled or DI water, with baking soda added to raise the KH to 4 dKH, we can get an indication that is far more acccurate than with the tank KH/pH readings. At least when the drop checker is green we can be sure the CO2 at that location is somewhere in the neighborhood of 20-45 ppm, not 4-5 ppm or 60-100 ppm. That gives us a good starting point for slowly increasing the bubble rate, a little each day, until the plants pearl an hour or so after the lights come on, and the fish don't all hang at the surface, seeminly gasping for air. It works well for that purpose. Of course once you see about what bubble rate you get when you reach the "good" level of CO2, the drop checker is of little use to you, except possibly for occasionally verifying that nothing has drastically changed in the tank.

Or, you can save pennies for awhile, and buy a $2000 CO2 probe.

 

[rodrigaj]

I know for sure that measuring the KH and pH of the tank water will not tell you how much CO2 is in the water, unless you are sure your water has nothing in it that affects either pH or alkalinity other than carbonates and CO2. None of us have that.

Vaughn- I have not tried to measure CO2 ppm for awhile now, so this surprises me. I always thought that those KH/pH/CO2 tables were OK to use. What other factors affect pH or alkalinity?

 

[argnom]

Thanks guys, that pretty much explains everything.

Cheers!

 

[Tom Barr]

Vaughn- I have not tried to measure CO2 ppm for awhile now, so this surprises me. I always thought that those KH/pH/CO2 tables were OK to use. What other factors affect pH or alkalinity?

Non carbonate alkalinity.
Peat/Tannic acids.
Certain phosphate buffers
Hydroxides

In some cases, the CO2 was 220 ppm according the chart using pH/KH test kits(pH meter calibrated and a KH test)

the reference KH in a drop checker gets around any of that, but then the pH measure stinks...........and there's a delay(seems to be about a 2 hour average for many folks).

Some do not have any issues with other errors with KH, so they get good results, others are wayyyyy off. Hard to say what specifically or tell, but it seems to cause some folks a lot of headache. Particularly if they rely heavily on test kits for any adjustments/ parameter targeting.

CO2 is just one of those things that varies a lot tank to tank, likely tap to tap.
It's central to hobby where it is used more than anything else. Algae, problem growth, pesky dust and algae that hangs on even though things look good on paper........fish stress etc........or deaths.........can all be traces very strongly to CO2, and it's really obvious if you have dealt with it afew times, but many are convinced that it's not it and seem very certain/sure of themselves about it even though I am not and cannot be myself, even with a 2000$ meter, I question it.

I know few things, but those things are pretty well demonstrated, CO2 is a SOB.
It has and will burn everyone at some point. If not today, give it some time.

Regards,
Tom Barr