Here is a good link to an article that explains the conversion cycle from ammonia to nitrite and then to nitrate. It is going to take a while for the tank to cycle so these article are good to read in the meantime. Helped me tremendously. Might be a bit over the heads of the younger students but the older ones should get some good out of it. Wow, this is fun.
Ammonia conversion to nitrate
Several years ago, I taught a class for electrical apprentices. It was second year which is very heavy on math and electrical theory. I had no idea how much I would enjoy watching the faces of the young (and not so young) men and women when they had that moment of understanding. Have fun.