X-ray fish care guide

X-ray fish (lat. Pristella maxillaris) is a fish kind of Characidae family. This is the only species of Pristella kind. The fish is a perfect choice for beginner aquarists, it is very undemanding and it can live in water with various parameters.

Habitat in the wild

This x-ray fish species is widespread in South America. It inhabits in Amazon and Orinoco rive basins and in rivers of Guyana. Quite often the fish can be encountered in inshore waters with brackish water. During rain season the fish migrates to flooded areas of fluvial plain (savanna, forest canopy) for spawning.

Scientific NamePristella maxillaris
Common NamesX-ray fish; X-ray tetra; pristella tetra; x fish
Range and habitatSouth America
Size4.5-5 cm (1,77-2 inches)
Lifespan5 years
Ease of keepingMedium
Minimum tank size80 liters (20 gallons) and more
Temperature21–27 °C (70–81 °F)
Water hardness5-20 dGH


In a tank the x-ray fish length doesn’t exceed 4.5-5 cm (1,77-2 inches). The fish lifespan is up to 5 years.

The fish body coloring is semitransparent, its skeleton and some internal parts of the body are clearly seen through its skin. Due to this distinctive feature the fish got its name.

The fish body is moderately long and flattened from sides with high back; this fish has a fatty fin. The fish translucent body coloring varies from olive to olive green with silvery tint; there is a black spot on the fish forebody. The x-ray fish has the same black spots on its lemon-yellow dorsal, anal and abdominal fins; dorsal and anal fins have white ends.

There are also albino fish species with red eyes and paler colored body, but it is quite seldom encountered on sale.

Difficulties in keeping

X-ray fish is easy both to keep and to breed. It is peaceful and suitable for any company of small fishes as well as it is rather enduring. The fish is undemanding in terms of food and it wasn’t observed when eating tank plants.

Care and keeping in a tank

The fish is plain and enduring, it can adapt to quite various water parameters. There are no special requirements as for tank decorations, it depends only on financial possibilities and imagination of its owner or on its tank mates demands.

This is a schooling fish, so to make sure that the fish feels comfortable you have to keep it in a school of 6 species in a tank of 50-80 liters (10-20 gallons) capacity. The tank should be thickly planted with tank plants to create shelters for the fish and floating plants will also be of some use; though don’t forget to leave some free space in a tank for the fish to swim.

Tank water parameters should be the following: temperature 72°F- 78°F (22 to 26 °C), ph: 6.0-7.5, 2 — 30 dGH. The tank maintenance consists of regular bottom substrate cleaning from organic waste (food leftovers, excrement) and weekly water renew (15–20% from the total tank volume) with fresh one.


X-ray fish is omnivorous and eats all type of live, frozen or artificial food. You can feed the fish with high quality flakes and give it bloodworm and brine shrimp to make the fish diet more balanced.

But keep in mind, that tetra species have small mouth and you have to choose food as small as possible.

Tank mates

This is a peaceful and schooling fish; keep them in a group of at least 6–10 species. The fish doesn’t like noisy and too active tank mates, but it is perfectly compatible with neon tetra, zebrafish, cherry barb.

Gender differences: male vs female

The female is fatter and larger than the male fish, it has rounded body, while the male is thinner and its abdomen narrows towards its tail stalk.


Any change of tank conditions (of course, a favorable one) triggers X-ray fish spawning. Water of average hardness and with neutral pH is good for the fish breeding. Tank water temperature should be 25 – 26 °C. A tank of 5-6 liters capacity and less can be used as a spawning tank.

The fish couple put in the tank will start spawning in the morning of the next day. If spawning process is delayed, keep the fish in a spawning tank for 1-2 days more. If you want you can feed the fish a little, for example, give it 3-4 bloodworms or coretra for each fish.

The eggs are small, transparent and not sticky. After spawning is over, you should put the breeders back to the community tank and leave the eggs for 5-6 days.

The juveniles require standard feeding. On the 6th day give them their first food. In spring, summer and autumn these will be pond microorganisms (daphnia, cyclop nauplii) and in winter – you should prepare infusorians in advance.

In a week you can feed the juveniles with larger live food: brine shrimp nauplii, cyclops and daphnia. The juveniles also eat Vinegar eels. Later on you can make the food size larger.

Juveniles grow comparatively slow. At the age of 6 month old they become 2.5-3 cm long and reproductive.