One of the best books I've ever read. This book is for the professional aquarist; it is certainly not for the beginner who wants book with more photos and less text. It has a very interesting and well-written chapter about the nitrogen cycle in the aquarium. The chapter includes chemical equations and tips; it includes information I've not read about in many other books. This is a serious book. Few of the subjects are: allelophaty between aquatic plants, plants as water purifiers, the bacteria in the aquarium, carbon (water alkalinity, pH, CO2, bicarbonate use, sediment CO2 uptake) and much more. As a student I found this book to be very professional, scientific, and interesting, I used this book when I had a test, and also when I had to write a work about water purifiers. As I said, it is one of the most rare kinds of books, and I recommend every person whom the hobby for him is not just 40 cm aquarium with plastic plants, to order it. It is a must have book.