What Do Goldfish Lose If They Are Kept in Dimly Lit or Running Water?

Goldfish need light and a stable aquarium environment to remain healthy.
i Goldfish image by Lucy Cherniak from Fotolia.com

Goldfish are hardy pets who usually get along well in small groups, making them an ideal choice for beginners. But even goldfish require basic care and tank maintenance and without proper lighting and water, they can suffer from serious health consequences.

Basic Husbandry

Goldfish live in cool lakes, streams and rivers with very mild currents. Keepers should mimic these conditions as much as possible. Unless the ambient temperature is very cold, your goldfish does not require a heat light; he does, however, require lighting. Most owners use a fluorescent bulb or an aquarium hood. Goldfish aquariums do require filtration, and the fish should not be housed in completely still water, as this water is more likely to become dirty and bacteria-laden. However, rapidly moving water can endanger your fish's health.

Pale Coloring

Goldfish depend on light to manufacture color pigments in their scales. Without adequate lighting, a goldfish's color can become extremely pale. Bright lighting causes more vibrant coloring. When inadequate lighting is combined with inadequate nutrition, goldfish may lose their color altogether.

Altered Behavior

Goldfish need light to regulate their circadian rhythms -- the daily cycle that regulate sleepiness and wakefulness as well as some behaviors. Without adequate light, goldfish may eat significantly less or may have difficulty locating food, resulting in malnutrition and health problems. When goldfish are placed in running water, they may also struggle to find food as they fight against the current. Running water requires goldfish to swim more forcefully, and this may lead to exhaustion and changes in behavior.


Light allows beneficial bacteria and algae to grow in a goldfish tank. Without these organisms, the tank may develop harmful bacteria, parasites and other microorganisms that can hurt your fish. The stress of running water may lower your goldfish's immunity, making her more likely to succumb to dangerous organisms growing in the tank. If you place your goldfish in a tank that has running water coming from the hose or the tap, the fish will be exposed to chlorine and other chemicals from untreated tap water. This could harm or kill your fish.

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