TankBud

Glass tetra

Moenkhausia oligolepis

Also known as Red-eye glass tetra

FreshwaterFish

Glass tetra (Moenkhausia oligolepis)
Silva-Oliveira C, Canto ALC, Ribeiro FRV · CC BY 4.0

Care at a glance

Temperature
75–82°F
24–28°C
pH
5.5–7.2
Adult size
2 in
5 cm
Minimum tank
18 gal
70 L
Temperament
Mostly peaceful
Social behavior
Schooling
Swim level
Middle
Difficulty
Easy
Breeding
Medium
Rarity
Common
Family
Characidae
Origin
Northern South America (Venezuela, the Guianas, Amazon basin)

Overview

Keep them in a group of at least six, and ten or more is better, in a tank of 70 liters or up with room to swim. They are mostly peaceful and sit in the middle of the water column. They can nip fins and pester smaller, slow tankmates when the group is too small or the tank is cramped, so a larger school spreads out that behavior. Keep water at 24 to 28 C, soft, and acidic to near neutral, ideally pH 6.0 to 7.0. Feed an omnivore mix of small flakes and pellets with frozen or live daphnia, bloodworm, and brine shrimp to improve color. Skip slow long-finned tankmates like bettas and guppies.

In the wild

Glass tetras come from northern South America, across Venezuela, the Guianas, and the Amazon basin, where they live in soft, slightly acidic blackwater. To match that, give them a tank stained with tannins from driftwood and dried leaves, a sand bottom, and dim lighting. Soft water on the acidic side, with pH around 6.0 to 7.0 inside the wider 5.5 to 7.2 range, brings out their best color. Hold the temperature between 24 and 28 C. They are active swimmers, so leave open room to move.

Good to know

This is a characin in the family Characidae, though FishBase now places it in the revised family Acestrorhamphidae. FishBase lists a wild maximum around 10 cm, but aquarium adults usually reach about 5 cm. It is an egg scatterer with no parental care.

Did you know

The common name comes from the silvery, semi-clear body, but the giveaway feature is the tail. Look for a dark spot at the base of the caudal fin paired with a bright reflective patch just above it, a marking that helps tell this species apart from similar silver tetras.

Weekly picks

Tank mates

Glass tetra is a mostly peaceful, schooling species that keeps to the middle. These picks share a community profile with it, are safe together in both directions, and overlap on water type, temperature and pH.

Check the full mix in the stocking calculator

Common questions

What size tank does a Glass tetra need?

A Glass tetra needs at least 18 gal (70 L). It spends most of its time in the middle.

What temperature and pH does a Glass tetra need?

A Glass tetra is comfortable at 75–82°F (24–28°C) with a pH of 5.5–7.2.

How big does a Glass tetra get?

An adult Glass tetra reaches about 2 in (5 cm).

Does a Glass tetra need a group?

Yes. A Glass tetra is a schooling species and should be kept in a group, not singly.

Related species