PREFACE

The goal of every serious aquarium keeper goes beyond simply displaying pretty fish. A dedicated aquarist strives to create a miniature ecosystem that showcases some of nature's most remarkable and spectacular creatures—freshwater and brackish water tropical fish. Unfortunately, many fish species are endangered or on the brink of extinction due to human activity. The destruction of rainforests, river damming, pollution, and the introduction of non-native species are among the primary threats to tropical fish.

Tropical rainforest waters are home to the majority of freshwater fish species. The Amazon Basin alone contains over 2,300 known species, with many more yet to be identified. However, the world's rainforests are under threat, disappearing at a rate of approximately one acre per second—equivalent to 116 square miles a day, or 42,340 square miles annually. Each day, an estimated 40 to 250 species become extinct, and up to 92,000 species may be lost every year. While tropical fish represent only a small fraction of the species disappearing due to extinction from deforestation, they remain at risk daily. Rainforest destruction impacts fish by reducing their habitat through erosion, disrupting weather patterns, and altering flooding cycles. Erosion increases sediment levels in the water, clouding visibility for fish that rely on eyesight and covering fish eggs, reducing hatching success. Marine fish are also affected, as sediment-laden rivers flow into the ocean, smothering coral reefs and forcing dependent species to relocate. Reading this passage will take about four minutes. In that time, 240 acres of tropical rainforest—formed over 70 million years—will have been lost forever. If deforestation continues at its current rate, these vital forests will disappear within a human lifetime. When they are gone, many of their irreplaceable treasures, both discovered and undiscovered, will vanish, leaving humanity with only regrets.

Dams also pose a significant threat to fish populations. Dams transform rivers, streams, and creeks into large reservoirs, permanently flooding forests and altering water conditions. Species adapted to river ecosystems must either adjust or perish. Additionally, dams obstruct the upstream migration required for certain fish to spawn. The devastating impact of dam construction on fish populations is evident in cases like the Aswan Dam on the Nile and the Amistad Dam on the Colorado River. Despite these consequences, many countries—including our own—continue to build dams in biologically rich environments.

Pollution is another destructive force caused by human use of river systems. The effects range from the slow, subtle impact of agricultural runoff to the immediate devastation of chemical spills that can wipe out entire river ecosystems. For instance, a recent cyanide spill in the Essequibo River in Guyana decimated local fish populations and threatened larger wildlife. Similarly, an oil spill on the Rio Napo in Ecuador severely disrupted one of the most biodiverse regions on Earth.

Even less dramatic human activities can have a profound impact on native fish species. The introduction of non-native species into waterways can be disastrous for local fish populations. For example, the introduction of the Nile Perch (Lates niloticus) into Lake Victoria as a food source has driven several Haplochromine species to extinction and severely threatened nearly all other fish species in the lake. In the waterways of Florida, foreign fish species—released by pet owners who grew bored or were unprepared for their pets' size—now overrun the ecosystem.

Less than 10% of freshwater tropical aquarium fish are caught in the wild. Overfishing for the aquarium trade is not a primary cause of declining fish populations, though some species have been affected by over-collection. For example, local fish collectors near Iquitos, Peru, report that their aquarium-bound fish catches are noticeably smaller than in previous years. However, commercial fishing for food remains the main driver of overfishing. Across the Amazon, food fish populations have declined in both numbers and size. For instance, the Arapaima—once commonly found exceeding 10 feet (3 meters) in length—is now rarely seen larger than 8 feet (2.45 meters).

Every aquarium enthusiast should be aware of the environmental conditions that impact the natural habitats of the fish they admire. We must all work to protect these ecosystems—not only for the sake of our hobby but also for the well-being of humanity.