Irregardless of where you live they are easily purchased on ebay. I have had very good luck with both Aquaticmagic eBay: Chame Co2 Drop Checker - Live Aquarium plant fish tank (item 250129017441 end time Jun-18-07 15:22:12 PDT) and Toponebrian eBay: Co2 Drop Checker - (99%)Look Like Elos (item 250129969791 end time Jun-20-07 08:57:13 PDT) The only thing I might add is that I have a preference for the Aquaticmagic Chameleon over the newer tear drop types. I personally feel they respond or react quicker to Co2 variations (larger throat orifice and greater volume for air gap), but they are both quality products from reliable vendors. The smaller tear drop type checkers are more discreet. FYI. always add an extra week to shipping time from HK post. It may very well get there sooner, but you won't drive yourself nuts waiting for it. Been there ! Done That !!

Depending on the reagent supplied, 5 drops of plain old bromothymol blue (commom low range PH test reagent) Mixed with a 4 dkh reference solution should supply an adequate color rendition for all intents and purposes within appx. +/- .05 ppm. HTH. Prof M