So, I'm not sure if you've mentioned it in another thread or not, but what's the purpose of the tank? Is for educational purposes and in what capacity? Or is it just a tank that you're putting up at work, in this case, a classroom?
I have 2 of those in my tank right now. Not very impressed so far. Both show very low level of ammonia (.5) yet a real test shows 2.0 ppm.Get one of those in-tank color changing indicators; don't remember the brand, maybe Seachem? you just place it inside and the color change will alert you but in no way it is a replacement for testing.