Co2 Drop Checker - Bromthymol Blue?

[satrop]

Hi all! So I am adding a CO2 drop checker to my tank. I'm pricing out the CO2 indication solution and if I'm right in thinking the CO2 indicator solutions other name is Bromthymol blue (the only ingredient in CO2 indicator solution)? Is the correct? Because if it is I can save a lot of money (relatively speaking) order that over CO2 indicator solution.
 
Over the counter: Fluval CO2 Indicator Solution = $8 for 10ml or!
 
Bromthymol Blue Indicator = $16 for 125ml. 
 
Also, could some one please tell me will a pH test solution do the same job? Because if thats the case then I can get a lesser know brand of pH solution for cheaper still.
 
Chemistry was NEVER my sting point.
 
Thanks in advance.

 

[daizeUK]

In a drop checker the bromthymol blue is usually mixed with a special solution of water that has a specific hardness of 4 KdH. 
 
The reason is that a drop checker works by measuring the acidity caused when CO2 gas dissolves in water.  In order to do this it needs the water to be a standard reference solution since everyone's tank water will have a different natural pH due to dissolved solids.
 
I don't know if it's possible to use other pH indicators but it's a problem of calibration - the brom blue + 4dkh solution is formulated to change colour at exactly the CO2 concentration we want for a planted tank, so you'd have to somehow calibrate your indicator to do a similar job.
 
You can either buy the bromthymol blue indicator and the 4 kdH solution separately or you can get them pre-mixed.  It's also possible to make your own 4 KDH solution.

 

[satrop]

Thanks for the help! Really helped me understand completely whats doing on. Ran down to the store and fetched some pH tester fluid, dropped that in with the 4 kdH solution and all is great.
 
I did just tweak my DIY CO2 kit a little. Added another generation bottle with a bleed off valve as to better control the bpm which is running at ~25bpm in a 10Gal tank. I have placed one of the CO2 generators into a warm bath to test the theory that a little extra heat will help, and it sure does, so I'll add another heater the whole set up just for the CO2 generators to keep them at a constant temp.