CO2 Calculation from 5-in-1 API Test Strip - The Planted Tank Forum
Old 06-02-2017, 06:08 AM Thread Starter
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CO2 Calculation from 5-in-1 API Test Strip

I am trying to find out the base level of CO2 in my tank before choosing a CO2 injection system. I have learned that CO2 can be calculated with KH and pH readings. While I found many conversion charts, I can't correlate my KH readings with them.

The API test strips I use measure KH by ppm (mg/L). Mine fall between 120 and 180, which the strips say is fine for a freshwater aquarium. In the charts I've found for calculating CO2, KH is only measured to about 20. None of the charts say what unit of measurement they are using for KH. They sometimes say what unit of measurement is used for CO2, but not for KH.

I feel like there is some conversion factor I'm supposed to use to correlate the reading from my strips with the CO2 conversion charts, but I have no idea what it is. I've included an image of the test strip chart and a CO2 conversion chart for reference. Any help would be greatly appreciated!

hufflepuffer is offline

Old 06-02-2017, 03:59 PM
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Your base Co2 level will be 2-3ppm without expensive testing equipment you will not know exactly but that chart is based on and most assume 3ppm at equilibrium. because your is in PPM and the chart is in degrees. your would be somewhere between 7-10 DKH on that chart based on the numbers you gave. I find liquid test kits more accurate.

Dan

Bump: What is your PH? I can give you a pretty good guess from that if its more accurate where your starting point is but really you should be using a drop checker with a known DKH solution. 4DKH is commonly suggested. Oh and the conversion is (your readingx0.056)

Dan
Dman911 is offline
Old 06-04-2017, 04:15 AM
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CO2 Calculation from 5-in-1 API Test Strip

You can find out your degrees by dividing the ppm always by 17.86. For example let's average you at 160ppm. That would give you 8.95 so say 9 degrees. You can do the same for ph and gh and so on.

I really do not like test strips. I only use the liquid tests. API is really good and you can usually see pretty accurately what it is.

The two best things to do are get a drop checker with solution as mentioned and check your ph right before co2 comes on and then an hour or so later when the lights will come on. You typically want a 1pt ph drop which should give you roughly 30ppm. Remember it's not exact and the drop checker will take a couple hours before reading what the actual co2 level is.

I found the best and easiest way is to get a ph pen. This once calibrated will give you very precise measurements and will save you test kit \$ in the long run. All you do is get a API kh test kit. Measure your kh. Then use the ph pen. Then go to http://aquariuminfo.org/co2calculator.html and punch in your ph, kh. It will tell you your ppm co2. Super easy. Here is a link to the ph pen I got that is one of the best investments for my planted tank. Mine was already calibrated. I verified it.
Jellas Pocket Size PH Meter / PH Tester / Mini Water Quality Tester for Household Drinking Water, Hydroponics, Aquariums, Swimming Pools, PH 0-14.0 Measuring Range, 0.1PH Resolution (Yellow) https://www.amazon.com/dp/B00YBUH4RC..._.J4mzbAFJ3B07

And the API kh test kit. API CARBONATE HARDNESS TEST KIT Aquarium Water Test Kit https://www.amazon.com/dp/B003SNDDAU..._4K4mzbKR1RQTJ

So in a nutshell \$20 will clear up all of the confusion for you so you can get to co2'ing

I know I jabbered on about more than you asked but maybe you could use the info like I sure did when I first went high tech.

Sent from my iPhone using Tapatalk

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Old 06-11-2017, 05:44 PM Thread Starter
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