I have one of those Ammonia Alert cards inside the tank, and noticed the color of the button looks different depending on whether the tank light is on or off. Light on, it looks yellow. Light off, pale green. The card has been in the tank for about a week. I'm out of the liquid test so I can't compare, have to pick some up tomorrow.
For those of you who use these, do you read them with the tank lights on or off? How reliable are they?
For those of you who use these, do you read them with the tank lights on or off? How reliable are they?