This book is, on the surface, something of a how-to manual for those interested in keeping fresh and saltwater aquariums. It should also serve to open your eyes to the wonders of the aquatic creatures and habitats that are to be found all around us and to foster an understanding of why they are important and what can be done to preserve them.
An aquarium can offer insights into worlds far removed from your everyday existence. Through the glass of an aquarium, even children living in the world's largest cities can become intimately acquainted with the lives of creatures that live thousands of miles from their homes. Although complex aquatic systems are discussed in this book, you will also learn about very basic aquariums designed to maintain common, hardy creatures. Something as simple as a glass jar housing a larval dragonfly can open up vast new horizons in your life.
This book reflects an ethical obligation to offer the best possible advice to those seeking to maintain aquatic creatures. Marine and freshwater fisheries the world over are collapsing, taking with them the livelihoods of many people. Species not directly fished are threatened by disruption of the food chain, and also because they are often collected, along with a species targeted by fishermen, as by-catch. Sea creatures that are important to practitioners of traditional medicine are also being harvested at unsustainable rates.
Pollution, industrial development, and the introduction of exotic species devastate both marine and freshwater communities, with coastal sea grass beds, mangrove swamps, coral reefs, and restuaries being particularly at risk. Freshwater habitats, because they are less able to self-clean than the open sea, are being compromised with frightening regularity. Many fishes and invertebrates are limited to very specific micro-habitats. Such species cannot easily relocate, and exterminated populations may not be readily recolonized. The information contained in this book will allow you to contribute to the survival of the threatened creatures of these ecosystems by providing them with proper care and breeding conditions.
On the opposite end of the spectrum, wide-ranging oceanic species are of particular concern because protection in one country does not guarantee safety in another. As you read about the complex reproductive strategies of these species, consider how long these behaviors have taken to evolve, how easily they can be disrupted, and how you can apply your newfound knowledge to help these animals. Each individual removed from its natural habitat is a significant event, and extinctions occur daily. It is possible that the cures for certain diseases are to be found in the body chemistries of aquatic animals — each species lost can therefore have devastating consequences for humanity.
Well-informed hobbyists can contribute significantly to what is known about aquatic animals. This is especially true concerning the less studied species, of which there are many. Scientists and researchers do not even know, to the nearest degree of magnitude, the number of species that exist. The information contained in this book will provide the basic groundwork for keeping a wide range of interesting animals, and will start you on your way to learning more. Especially important is sharing your knowledge with others. Publish your observations in the newsletters of local aquarium societies and cooperate with aquariums, museums, and other such institutions. In these times of decreased budgets for scientific institutions, the help of dedicated volunteers is vital. Conversations with professionals working in your area will often lead to a variety of interesting opportunities.
Above all, enjoy your hobby, continue to learn, and share your passion with others.

