# Good CO2 test kit?



## mark546 (Sep 12, 2013)

If you have a red sea drop checker use 4dkh fluid and the ph reagent from your ph test kit.

Otherwise order a kh test kit and use the co2 chart.

Although if you have anything in your tank that alters your ph like drftwood the chart is way off. According to the chart I have 120 ppm co2.

If you use an atomizer or diffuser a bubble counter wont be accurate. Mine is pretty close to yellow and I m fairly certain I am not overdosing at 3 bps in my 55.


----------



## zimbo (Oct 8, 2011)

any major differences between KH solution (which i have) and 4dkh?.....the latter is not something in my test kit..I guess i'm a bit confuzzed, can anyone else chime in? With about every other person throwing out what their CO2 ppm is around here, I'm sure there is a relatively straight forward calculation/test. IT seems there isn't much in terms of a commercial test made per se (from what i can find) so there's obviously a bit of the puzzle missing here that i can't phathom in how to test it. I do need idiot proof instructions........!!


----------



## Hoppy (Dec 24, 2005)

There is no accurate way to measure the ppm of CO2 in a typical aquarium. You can measure the carbonate hardness and the pH, and use one of the charts that are available to see what the ppm of CO2 would be if the water had nothing in it that affects pH, except for CO2 and carbonates, but that very, very often gives a number that is much higher than the actual value. You can use a drop checker, but the accuracy of that is low because of the difficulty in judging the color of the water in it. Or, you can buy a very expensive CO2 test probe - $1000+ - but that seems ridiculous for an aquarium hobbyist.

So, rather than try to determine exactly how much CO2 is in the water, it is best to try to find out if you have about the right amount of CO2 in the water to make the plants grow well, and not harm the fish. To do that you need to slightly increase the CO2 bubble rate, watch the plants and fish for a few days, and repeat until the plants no longer do better after the increase, or until the fish show signs of obvious distress.

Even if we could easily measure the ppm of CO2 in our aquarium, we still don't know what the optimum ppm of CO2 should be. The more light you have - the higher the PAR - the more CO2 you need, and not all plants need the same amount of CO2. The more oxygen you can keep dissolved in the tank water, the more CO2 the fish can live with.


----------



## dmagerl (Feb 2, 2010)

Does anyone know if this is any good?
Hanna Instruments HI3818 Carbon Dioxide Test Kit, For Approximate 110 Tests: Amazon.com: Industrial & Scientific
Hanna Instruments HI3818 Carbon Dioxide Test Kit


----------



## zimbo (Oct 8, 2011)

Thanks for the input Hoppy.

pH out the tap here is 8.0, I drop it to 6.5 with CO2. I tend to pH control rather than run it at so many drops per second. 

I have liquid rock here. GH is right now is 120, and comes in at 130 out the tap. 

Current KH is about 40 which per a calculator i found gives 370ppm....and the fish are perfectly happy, and i have never seen an iota of pearling in this tank. 

Should i be dialing back the CO2 then?


----------



## Hoppy (Dec 24, 2005)

You don't have anywhere near 320 ppm of CO2 in the water. That much would be fatal to all of the fish, very quickly. That is why you can't calculate the ppm of CO2 from KH and pH. If you want to use the pH controller, just slightly lower the pH set point, wait a few days, while watching the plants and fish. If the plant do better, and the fish don't show distress, repeat this every few days. This will let you slowly creep up on the optimum CO2 setting, whether measured by pH or bubble rate. Assuming you have medium lighting or more, the plants should start pearling when you have a good CO2 level, and/or they should grow faster and look better. Fish distress, in my experience, is fish clustering in a corner at the top of the tank, apparently gulping air. At that point fish deaths will soon occur if you don't drop the CO2 level a bit. Some fish just lay on the bottom, and their color fade out, when they have too much CO2.

The problem with a pH controller used this way is that any rise in KH will cause you to have too much CO2, so be sure your KH is stable before trying this.


----------

