X-Ray Tetra (Pristella maxillaris)

The X-Ray Tetra (Pristella maxillaris), also known as the Pristella Tetra or Water Goldfinch, is a small characid from coastal drainages and the Amazon/Orinoco systems of Venezuela, Guyana, and Brazil. Its most distinctive feature is its translucent body — the skeleton and internal organs are visible through the skin, giving it its common 'X-ray' name. Despite its transparency, the yellow-tinged dorsal fin with a black and white pattern, and red-orange tail fin add subtle but attractive coloration.

This is one of the hardiest and most adaptable of all tetras, tolerating a remarkably wide range of water conditions including slightly brackish water in its native estuarine habitat. This hardiness makes it an excellent choice for beginners and for aquariums with a wider range of water parameters than typical soft-water tetras.

X-Ray Tetras are active, peaceful schooling fish that thrive in groups of 8 or more. They occupy the mid-water zone and display the typical tight schooling behavior of small tetras, which is particularly striking given their translucent bodies. An albino variety lacking even the slight body pigmentation is also commonly available.

They are omnivores that accept a wide range of small aquarium foods readily and are undemanding in their care requirements.

Water Parameters: One of the most adaptable tetras: pH 6.0–8.0, temperature 22–28°C, GH 4–20. Tolerates slightly brackish water (1–2 tsp salt/10L). Wide tolerance makes it suitable for many aquarium setups including community tanks that aren't specifically soft-water. Regular water changes of 25% weekly.

Tank Setup: Minimum 60 liters for a school of 8. Planted aquarium with open swimming space in the center. Dark substrate and subdued lighting enhance the appearance of their transparent bodies and subtle coloration. Good filtration with gentle to moderate flow.

Feeding: Omnivores that accept quality micro flake food, micro pellets, frozen bloodworm, daphnia, and brine shrimp. Feed twice daily in small amounts. Not picky — one of the easiest tetras to feed.

Tankmates: Ideal community fish compatible with virtually all peaceful species in the appropriate size range: other tetras, rasboras, corydoras, small gouramis, and dwarf cichlids. Their transparent appearance is complemented by more colorful schooling species in a mixed community tank.

Health: Hardy and disease-resistant. One of the most forgiving tetras for beginners. Watch for ich and bacterial infections if water quality drops. Maintain stable conditions. An excellent, low-maintenance schooling fish.