My talk is an introduction as to how knowledge of the natural environment drives the development of the physical, chemical, and biological structure and maintenance of aquariums and propagation systems. The essence of marine aquaristics rests deep in the heart of the natural marine environment. Understanding the chemical, physical, and biological complexities of the marine environment makes it possible to create as complex a marine microcosm as a 200 gallon reef aquarium and a marine aquarium as basic as a 10 gallon clownfish tank. It isn’t necessary for a beginning aquarist to have a complete knowledge of the complex functions of captive and natural marine systems to be successful; but they do have to follow the instructions of those that have that knowledge, and also strive diligently to learn not only the how but also the why of the constructions and mechanics of the modern marine aquarium.