eBay Drop Checker arrived, but...

If the "blue water" you refer to came in a small, 10ml dropper bottle, then that is your indicator solution.

You need to mix up (or buy from Bill) a 4KH solution. Add a couple ml of that to your drop checker then add a couple of drops of the blue indicator solution that came with the drop checker.

You will notice color changes in an hour or two.

 

If you have a pH test kit that gives a yellow color at about 6pH and blue at about 7.2 pH, such as the Aquarium Pharmaceuticals test kit, you can use that test reagent. I am not impressed by the reagent sent out with the ebay drop checker. From what you are describing I wonder just what the stuff in the bottle you have really is. Bromothymol Blue indicator, which it should be, is yellow in the reagent bottle, but turns blue in typical tap water.

 

I got the same thing you did I think. Did it come in a white bottle with green lettering?

It seemed to work for me in the 4KH reference sol'n, but it's tough to tell exactly what pH you're at since each color change indicates a 1 pH step.

I just changed out to bromo blue last night and I think its easier to get a more accurate reading with it.

At 30 ppm CO2 in 4Kh solution you will have a pH of 6.6 which is right in the good range for bromo blue.

 

I got my KH standards from Bill. You can find more info on them in the Sale/Swaps forum. He's got a thread called "KH Standards" with more info on. It was fast and reasonably priced.

The bromo blue I got was the Red Sea CO2 checker drops (I'm pretty sure its bromo). I got it from my LFS for $3-4 for a 10ml bottle.

Does anyone know if the Aquarium Pharmaceuticals "pH Indicator Solution" is bromo blue? It seems about right because the indicator card that comes with it shows a color change from yellow at 6.0 to dark blue at 7.6.

The Aq Pharm pH checker runs about $5 for 1.25oz (37ml). You can find it at many LFS or online at places like Big Al's and That Fish Place. It may be a cheaper option than the co2 checker drops, plus it comes with a color chart. You'd probably want to check it against a standard to get a more accurate idea of what pH the colors match up to.

Tom Barr and others may know of cheaper sources of bromo blue.

 

The AP pH test reagent is bromo blue. It's the one I use. It is possible to buy bromothymol blue from chemical supply places, but what you get isn't a test reagent. It is a dye, which you then have to mix your own reagent with. Maybe it's cheaper, but it sure is a lot more work for a lot more reagent than you could possibly use.

 

i have the red sea drop checker and it tells me to use 1 ml of the aquarium water and the two drops of the reagent. should i also use the 4KH solution and not the aquarium water?

 

Yes use a 4KH standard. Your readings will be more accurate. Other substances in your aquarium water can change the pH and could give you a different pH reading for a given CO2 concentration.

There are quite a few good links that can give you lots of details if you want to read more. Here are two for you to start with.

http://www.barrreport.com/articles/2661-drop-checkers-co2-indicators-why-how.html

http://www.barrreport.com/co2-aquatic-plant-fertilization/2289-old-co2-idea-good-new-idea.html