Independent variables in an experiment are the part that we change to get a desired outcome. In a reef aquarium it's coral health, coloration, and growth rate that we're searching for. Even as a science teacher I've found myself changing multiple things at the same time. So I can never quite tell which variable changed made the most significant impact. Just recently due to some elements low in an ICP test, I dosed potassium, boron, iodide, fluoride and a little bit of iron. The reef looks significantly better. Near around the same time, I increased the intensity of my lights just a little bit and added a little more red to the spectrum. Needless to say I can't tell what variable tested has made the most significant impact. Question is, do you find yourself changing multiple variables at the same time, or are you patient enough to test one independent variable alone and make the proper observations? Or, is it just the nature of the game and reacting to ICP tests?
