pH test color

[Telepath]

How do you determine pH if you keep a tank of tetra's and use a "black water "treatment . pH color of 6.6 to 6.8 is slightly yellow. Would a eletronic pH monitor be better?

 

[Blinky]

I'm assuming you're having trouble because your water is yellow going into the test tube as a result of the black water treatment. Your water may still change colour enough to read the test, but if not I think there may be tests that use another reagent (and, therefore turn a different colour) available.