The Planted Tank Forum banner
1 - 9 of 9 Posts

·
Registered
Joined
·
94 Posts
Discussion Starter · #1 ·
I've tested my 4dKH drop checker water and found out that it is actually 5dHK water.
Question is......whats my Co2ppm when the solution inside the drop checker is reading green?
Is there a chart?
 

·
Banned
Joined
·
5,009 Posts
Since Bromothymol blue is a pH indicator, your 5 dKH solution will be green when the pH is ~ 6.6. Then using the CO2/KH/pH table, you would have ~ 38 ppm of CO2.
http://csd.net/~cgadd/aqua/art_plant_co2chart.htm

Actually the green color may be visible from pH's of ~ 6.4 to 6.8 with the corresponding CO2 levels of ~ 24 to 60 ppm.

 

·
Banned
Joined
·
5,009 Posts

·
Registered
Joined
·
94 Posts
Discussion Starter · #5 ·
Just got back home and tested......
I have a Ph @ 6.5 and a dKH @ 4degrees.
Gives me 37.947ppm Co2 in tank which is high.
Now what? De-gas with airstone?
 

·
Banned
Joined
·
5,009 Posts
Just got back home and tested......
I have a Ph @ 6.5 and a dKH @ 4degrees.
Gives me 37.947ppm Co2 in tank which is high.
Now what? De-gas with airstone?
You can't use that chart/calculator to calculate the amount of CO2 in an aquarium. Chuck explains why in that same link.

The CO2/KH/pH relationship is based on carbonate/bicarbonate buffers only. You have phosphate buffers with other acids and bases in an aquarium that throw this relationship off. This gives false levels of CO2 concentration that are skewed to the high side. This is why you use the known dKH carbonate based buffer in a drop checker along with the low range freshwater pH indicator solution. This gives a good approximation of the CO2 level in an aquarium.

Gives me 37.947ppm Co2 in tank which is high.
Your actual CO2 level is actually lower than this.
 

·
Registered
Joined
·
94 Posts
Discussion Starter · #8 ·
Allright so if my tank water is @ true(or tested true) 4dKH....Then I can't use that water as the solution in the checker because of the false readings due to phosphate and misc buffers.......Right?
I'm kinda liking this hobby more and more!
 

·
Super Moderator
Joined
·
12,008 Posts
Allright so if my tank water is @ true(or tested true) 4dKH....Then I can't use that water as the solution in the checker because of the false readings due to phosphate and misc buffers.......Right?
I'm kinda liking this hobby more and more!
Correct. A "4 dkH" result from your tank water can be due to a combination of other buffers (not just the carbonate buffer). As the pH/kH/CO2 relationship works on the basis that the only buffer is carbonate/bicarbonate, you cannot use your tank water in your drop checker, even if it is "4 dkH".
 
1 - 9 of 9 Posts
Top