Unlike other animals, fish cannot get up and walk away from a dangerous situation. When toxins are in their aquarium water, accidental poisonings can occur. However, keeping the water clean, regular water changes of 20 percent once a week, and testing the water for toxins on a regular basis should prevent poisoning problems in your aquarium.

Some of the most common toxins found in aquariums come from tap water. For example, if you use tap water and you have copper pipes, copper, which is toxic to fish, is introduced into the aquarium. Untreated tap water can also introduce chlorine and heavy metals into the aquarium. In addition, fish produce their own toxins simply by swimming around their aquatic environment and excreting wastes into the water.

Cigarette smoke can also be dangerous to fish, as can other poisons that are introduced into the aquarium through the air, such as paint fumes and household cleaning products. Plastic buckets can also cause problems if they are used for household tasks such as mopping the floor and are then used with your fish. To prevent this type of poisoning, designate a bucket strictly for aquarium water changes.

If your fish display any of the following symptoms, check your water quality immediately and treat as necessary.

Symptoms

• Breathing problems, such as gasping just below the surface of the water, rapid or shallow respiration.
• Shakiness in movement
• Violet-red, very red or swollen gills
• Fading of color
• Shooting "madly" through the aquarium
• Disrupted equilibrium
• Paralysis
• Twitching
• Bumping into things
• Red spots on the body
• Cloudiness of the skin
• Increased mucus secretion
• Malaise
• Fins clamped together
• Swimming on the side
• Standing on the head
• Turning over
• Loss of appetite

Common Poisons Found in the Aquarium

• Ammonia
• Chlorine
• Hydrogen sulfide
• Carbon dioxide
• Ozone
• Insecticides
• Antibiotics (used over long periods of time)
• Egg disinfectants
• Metals (such as aluminum, iron, lead, mercury, nickel)
• A pH that is too high or too low

Diagnosis

1. Unusual smelling water: Some of the common smells that can reveal the presence of a toxin are: the smell of chlorine, a "rotten egg" smell or an "electrical/metal" smell.
2. A water test kit can quickly help you identify poisons in your aquarium.
3. If you cannot diagnose the problem on your own with a standard test kit, take a water sample to a professional and ask for help in analyzing the water. Professionals have many additional tests available and they can help you diagnose the problem. Your local PETCO store provides free water testing.

Treatment

1. Once the offending substance is identified, purchase the proper chemicals and treat the water accordingly. Water changes of 30 percent or more may also be required for treatment.
2. Check your filters and change them if necessary.

Prognosis

FAIR - Most poisonings can be identified successfully with regular water checks and treated. Sometimes, though, the substance is not identified in time, which results in mass mortalities. Metals are especially dangerous because they build up in the fishes' internal organs and there are very few evident symptoms until it is too late.