What Makes a Tetra Swim in a Circle?

Tetra fish come in a wide variety of colors and grow to only 1 1/2 to 2 inches in length and are generally easy to keep, even for beginning aquarists. Occasionally, tetra can succumb to diseases, such as neon tetra disease, which cause the fish to swim in circles. As with other fish, maintaining the right water quality is important in preventing tetra fish diseases.

  1. About Tetra

    • Tetra fish belong to the family of fish called Characidae, a fresh water variety that inhabits the waters in South America and Africa. Tetra are toothed, and the name reflects the shape of these teeth. Neon tetra are among the most popular species of fish bought for home aquariums. The neon tetra has an iridescent blue line that runs along the side of the body from the nose to the rear fin, with another red line that runs alongside it. Neon tetra fish create a very colorful display in home aquarium tanks. However, problems can develop with tetra fish.

    Swim Bladders in Fish

    • The swim bladder is a small internal organ in tetra fish that contains air and allows the fish to maintain its buoyancy. The walls of the swim bladder expand and contract according to ambient pressure, allowing the fish to adjust his relative position in the water very quickly. When disease or injury occurs in the swim bladder, the fish has difficulty maintaining balance or direction. These problems can cause unusual movements such as swimming in circles or leaning in a lopsided manner.

    Tetra Diseases

    • Tetra fish can acquire diseases from new fish that are introduced to the tank. Isolate new fish for a period of three to four days and observe them for any signs of parasites, such as white spots or black granular nodules on the skin. Neon tetra disease frequently strikes aquarium fish. This disease is cause by a sporozoan called Pleistophora hyphessobryconis, according to the Aquatic Community website. Leaving dead fish in the aquarium, which the other fish will consume, often spreads it. It is important to remove any sick or dead fish from the aquarium to prevent further spread of the disease. Symptoms include dull coloration of the skin, restlessness and difficulty swimming. There is no known cure for this disease, so careful maintenance of the water and removal of affected fish is strongly recommended.

    Tetra Care

    • Tetra originate from a warmer climate, so the aquarium must be kept in the range of 75 to 78 degrees Fahrenheit. An aquarium heater and thermometer is required to keep the water temperature in this narrow range. Tetra will lose their deep color in hard water and are prone to more diseases when water is kept at a high pH. A pH range of 6.8 is recommended, according to the Tetra Fish Care website. Tetra are social fish that become unhappy and ill in isolation, so keep them with other fish.