Nutritional deficiencies are difficult to diagnose in most aquatic creatures. An improper diet may manifest itself in poor or deformed growth and a failure to reproduce. Unfortunately, we know little of the nutritional requirements of many fish and even less concerning invertebrates. See Chapter 16 for more information about nutrition.

Unfortunately, many of the diseases that affect captive fish and invertebrates cannot, at this point, be cured. Because many such conditions can lead to a lingering and painful death, you may wish to consider euthanasia for your terminally ill pets. Fish anesthetics can be used to quickly and humanely euthanize animals afflicted with incurable diseases. At present, these are available only through veterinarians.