To offer your fish a healthy environment, a certain understanding of their behavior and of the biological and chemical factors that affect them both in their natural habitat and in the aquarium. The home aquarium is just a " piece of portable nature" only to a limited extent; it should rather be considered as an artificial and even also artfully arranged garden.

Most aquarium fish come from the tropics, where they live in extremely clean waters with low conductivity and hardness, high oxygen content, and often with many dissolved organic substances. Today, while it is quite possible to chemically adjust aquarium water to match the fish's natural waters, it is hardly possible to approach their degree of cleanliness. In the aquarium, however, polluted water, harbors microorganisms that are harmful to the fish. Many of these organisms are bacteria and fungi that normally live on the bottom of the aquarium or in the water, but they also can cause disease. In the wild, where the fish lives in large quantities of water, it is not often confronted with such organisms. In the closed system of an aquarium the disease-causing organisms multiply. The fish is constantly picking them up, and its body is continuously attempting to stop these organisms from multiplying. The fish easily succeeds in resisting them if it is fed well and if it feels at home in its aquarium and that has proper water quality and care.

    Behavioral Disorders
    Locomotor Disorders
    Fhysical Changes
    Changes in Color
    Gills
    Skin

Feces
Blood
Body Cavity
Gill Filaments
Spleen Heart & Gonads
Liver and Galblader
Intestines

Swim Bladder
Kidneys
Brain & Muscles
Egg & Broods
Cysts
Bacteria

Just as in waters in the wild, the aquarium also has a biological self-cleansing cycle. You must recognize and foster this process in order to effectively care for the water in an aquarium. There are many books on water chemistry and aquarium hygiene. The better this process of self-cleansing is achieve and keeping the water quality high for longer periods. Books on the subject allow the interested hobbyist to independently yet effectively increase his knowledge of aquariums.

With good hygiene, you can make it tough for the disease causing organisms to survive. Immediately remove any dead or sick fish, regularly vacuum out any accumulations of debris from the bottom crevices and from the nooks and crannies of any landscaping. The bacterial count in the water can be significantly lowered by use of an ultraviolet lamp in the filter.