Hi poindexter, test kits are absolutely vital to know whats going on in your tank. If you can afford a master kit or even a basic master kit with the main 3 (ammonia, nitrite and nitrate) its cheaper than buying all the tests separately. Other tests like PH, GH, KH can be added later to fine tune your tank. Everytime a fish may look sick or is acting strange water tests should be done before using any medications. Laughncat, I agree some of the colours in the charts are very close but I think the main thing is that 0ppm reading should be clear to read and not simular to any other colour. For example ammonia should only ever be crystal clear, anything else and its too high. Nitrite should only ever be light blue and nothing else. This is my test negative colours and the only colours I,m really interested in anyway. Anything else is not acceptable. (Test colours may vary from brand to brand).