X-Ray Tetra
(Pristella maxillaries)

The x-ray tetra or Pristella maxillaries is a wide bodied fish that is popular among aquarium owners because of is translucent body. X-rays have an iridescent sheen to them under aquarium lighting. They are a smaller variety fish reaching only 1.5 to 2 inches in length. Males tend to slimmer than females.

Since this is the last article on tetras, we will review them as a family. Tetras are members of the family Characidae more commonly known as characids. They are endemic to the Americas. They inhabit the freshwaters of southwest Texas through Central all the way down to South America. Many are native to the Amazon River. Characids have a life span of approximately five years.

Tetras are a peaceful, hardy fish. They make a good choice for novice aquarists. They make suitable community fish but have a tendency to be fin nippers. This behavior is more prominent in larger groupings. Avoid mixing large finned species such as angelfish, bettas and fancy guppies with tetras.

Tetras are extremely social. They are shoaling fish. Shoaling fish function best in a group. They may survive in an aquarium without other members of their species but it is not recommended. You will want to keep at least four tetras. Six or more is ideal.

Tetras come in several varieties. Some are slender bodied like cardinals  and neons . Others have wide bodies. Black skirt and bleeding heart tetras are among the wide bodied variety along with x-ray tetras. There are three translucent tetras commonly sold in fish stores. Theses are the red phantoms, the black phantoms, and of course the x-ray tetra. There is even a species commonly referred to as a cave tetra. These fish have dwelt in a light-less environment for so long that they are blind. Tetras have been selectively bred by the aquarium trade industry. The golden neon tetra is a very popular result of this selective breeding.

Tetras thrive in soft, slightly acidic water common the rivers of South America. The ideal pH level is around 6.8. They prefer water temperatures between 72-77 °F but will easily tolerate temperatures from 70-80 °F.

Tetras are omnivorous. They can be fed a diet consisting entirely of common variety tropical fish flakes. But a diet high in protein will help them maintain their vigor and body color. A diet high in protein will also help to initiate their spawning cycle. They will readily eat brine shrimp, tubifex, bloodworms, frozen and freeze-dried foods. Small amounts of powdered eggs are a good alternative to store bought protein based foods. Do not over feed them if you choose powdered eggs. You will foul up your water.

Tetras are a prolific species. It is not uncommon for their population to double in just over a year in the wild. With the exception of the bleeding heart tetra, tetras are rather easy to breed in captivity.

Tetras can be induced to spawn when provided with a suitable environment. They will require soft water, slightly acidic water. Water softness can be achieved by filling the breeding tank with bottled of reverse osmosis filtered water. Water acidity should be around pH 6.5. Ph levels can be altered chemically. A natural solution is to filter the water through peat. Or you can add a thin layer to the breeding tank substrate. Peat releases humic acid into the water raising acidity levels. Make certain the peat contains no fertilizers or chemical additives.

Subdued lighting is essential for two reasons. Tetras are less apt to spawn under bright lighting. Tetra eggs are vulnerable to fungal growth. Intense lighting promotes fungal growth.

Tetras are egg layers who scatter their eggs. Characids do not demonstrate the parental instinct found in fish such as cichlids. Cichlids will guard their eggs whereas tetras will eat them. A good trick to insuring a maximum survival rate is by adding a layer of marbles to the bottom of the aquarium. Their eggs sink. They will slip down in between the marbles and out of the reach of adults. Adult tetras should be removed from the breeding tank immediately after spawning.

Hatching time is typically 24 hours. Fry will become free swimming in 2-3 days. Fry can be fed newly hatched brine shrimp or liquid fry food formulated for egg layers.