We are studying the Carbon/Oxygen cycle, the Nitrogen cycle, and the water cycle in science. We have been testing the water quality of our Brook Trouts for Ammonia, Nitrites, Nitrates, and pH too. So far the fish are doing well. They have visible fins and are very actively eating.
In the experiment, we added drops of Bromothymol blue solution to water, added CO2 with our breath, and watched the solution turn pale yellow as the Carbon Dioxide entered the water!
All that was missing was elodea, a water plant that is no longer sold in stores (for it is an invasive species). The original idea was to let the plants' photosynthesis turn the water blue again. It hasn't worked too well in the past, and it is about as exciting as watching paint dry, so we just stayed with the immediate reaction of adding CO2 to the water and watching it change color.
