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Discussion Starter · #1 ·
I believe the commonly used CO2 calculator found on this site http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm is frequently used and discussed on this (and other) forums with regards to CO2 levels and its relationship with kH and pH.

The article states "CO2/pH/KH calculator and chart

NOTE: This calculator (and the chart based on this formula) will only work if your water is carbonate buffered. If your water contains high levels of phosphates, it will alter your water properties, and invalidate these CO2 calculations."

If I'm using CO2 injection with EI dosing, I'm adding excessive amounts of kH2PO4 (Mono Potassium PHOSPHATE) in addition to other ingredients. Well, my phosphate level is going to be high and therefore invalidate the CO2 calculator. How do I resolve this problem so I can calculate CO2 levels properly.
 

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I think most people on the forum use drop checkers or other means to estimate their CO2 levels. The pH KH chart is not very reliable.

The old ph/kh chart is very inaccureate so most no longer use it. There are just too many things that throw this chart off.
 

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I'd be surprised if the amounts of PO4 we add to our tanks (1-5ppm at most), will impact the CO2 charts that much.

Here's my 2 cents worth: yes, the best way to measure it is via a drop checker, but that means you must be sure you have 4kh water in the checker. If all you have to go by is Chuck's chart, then use it as an approximation and plan to undershoot your CO2 levels a little so you don't od your fish. The plants will be very happy in 25ppm CO2. Another method to estimate 30ppm CO2 is by taking a sample of your tank water, and measuring the pH. Then let that sample sit out at room temperature for 24 hours. If you have 30ppm the pH will rise by 1.0unit, approximately. (pH in tank 7.0, after de-gassing and equilibrating in the room 8.0 equals approx 30ppm CO2).

I have gone both routes. I have a drop checker and verified that both other methods, in my tanks give me approximately the same values. I keep my PO4 level in the 2-4 range, and have lots of driftwood.

My 2 cents. :)
 

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Right on Bert H
 

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Funny- I was surprised at all the drop checker traffic and thought most people used the pH/kh chart method!

Maybe a poll is in order?
 

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Discussion Starter · #6 ·
From Chuck's Site:
If your water contains high levels of phosphates
Bert H:
I'd be surprised if the amounts of PO4 we add to our tanks (1-5ppm at most), will impact the CO2 charts that much.
Well, my Phosphate test kit & card reads ppm 0.0, 0.25, 0.5, 1.0, 2.0, 5.0 and 10.0. A week after I did my last 50% water change and stopped CO2 and adding ferts, mine read 5.0 (on the high end of the scale).

So what is "high levels of phosphates". What would mine have been had I measured it in the middle of the dosing week?
 

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It's not just phosphates that throw the chart off. I have measured in my tanks and found upwards of 50-60ppm of co2 according to the chart. Now we know that fish can not live with this and they where showing no sign of being stressed. Logical conclusion, I did not have 50-60 ppm co2. And I kept getting signs of low co2 by algae that was forming and plant growth. This system has two floating variables with not controlled base line. With the drop checker there is a set in stone 4dhk base line (if the mixture is correct and made with distilled water) so we know that a given amount of co2 will have a known effect. When I started to use the drop checker my suspicions where correct, way to little co2. Things in my tank immediately got better, more growth and less algae. This is why a lot of people do not use that chart any more. It is accurate if there is nothing to throw it off but in a planted aquarium it is almost in possible to keep that standard, even some fish foods will effect this reading. With the drop checker there is no contact from the aquarium water and the 4dkh water so no chemical in the tank will effect the reading. This is not a perfect system for measurement but it is a LOT better than the ph/kh chart and cheaper than a co2 meter.
 
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