pH testing with Bromothymol Blue - Quantities?

[Braam Moolman]

Good day all,

I'm trying to figure out what ratio I should add Bromothymol blue : water to test pH...

2drops Blue : 2ml water?... or more water? Google gives no definitive answer pertaining to aquaculture or in this case AP. Results I found varies between 2ml to up to as much as half a cup

Hope someone can advise please

Thanx in advance