# Bromothymol blue



## StevenA (14 Feb 2008)

I have just bought some 4dKH solution from Aquaessentials.co.uk, and it says on the bottle that i can only use Bromothymol blue solution with it. I have a Red Sea Co2 indicator in one of my tanks, and was wondering if the solution that came with that is Bromothymol blue, but it doesn't say anything about the ingredients on the bottle.


----------



## ceg4048 (14 Feb 2008)

Hi Tourney,
                   I reckon you can figure out if it's bromo blue based on the colors that it produces in it's tests. Bromo blue produces a blue color in the test vial when the water sample is alkaline (pH >7), various shades of green color when the test sample is neutral to slightly acidic (pH 7 to 6) and yellow when the test sample is very acidic (pH<6). If these are the colors on your color chart that came with your kit then you certainly have bromo blue.

Be sure to check out this CO2 measurement article: http://ukaps.org/forum/viewtopic.php?t=467

Cheers,


----------



## George Farmer (14 Feb 2008)

I'm fairly sure the Red Sea stuff is bromo blue.


----------



## StevenA (14 Feb 2008)

Thanks for the reply's ceg4048, and George. I did a search on Google and found another forum (sorry but i forget the name of it), and there was a post on it where the guy had used the Red Sea reagent in an ADA style drop checker, using 4dKH solution,  and he had good results with it, so i'll give it a go.   

Just one more question, is it possible to make my own 4dKH solution using DI or RO water and adding bicarbonate of soda to it a little at a time and checking the results?


----------



## George Farmer (14 Feb 2008)

Tourney said:
			
		

> Just one more question, is it possible to make my own 4dKH solution using DI or RO water and adding bicarbonate of soda to it a little at a time and checking the results?



Yes.  Some make their own solution up.  You need accurate scales though.  The recipe is on the net somewhere.


----------



## sks (15 Feb 2008)

I use 0.12g of Bicarbonate of soda per litre. Of course you are not going to get this accuracy of measurement so I fill my water storage tank with about 270 litres of RO and add the bicarbonate accordingly. I decant half a litre into a bottle and the rest is used in a water change after GH hardening.

The Rea Sea CO2 test is strange since they recommend you use the tank water, maybe their indicator fluid has a wider KH tolerance band, but they warn you not be use anything less than 4 KH.


----------



## ceg4048 (15 Feb 2008)

Hi,
    In my opinion it's better to ignore the Red Sea recommendation regarding the use of tank water. If you put tank water in the drop checker you may as well not use a drop checker at all. You'd be measuring the pH of the tank water which is corrupted with other acids. The pH/KH/CO2 relationship is therefore invalidated when the pH is influenced by any acid other than the carbonic acid formed when you inject CO2. 4 dkh water made from RO or distilled water isolates this test sample from the effects of other acids in the tank.

Cheers,


----------

