TankBud

Threadfin glassfish

Gymnochanda filamentosa

Also known as Filament glassfish, Filament-finned glassfish, Long fin glass fish

FreshwaterFish

Threadfin glassfish (Gymnochanda filamentosa)

Care at a glance

Temperature
73–81°F
23–27°C
pH
5.0–7.0
Adult size
1.6 in
4 cm
Minimum tank
16 gal
60 L
Temperament
Peaceful
Social behavior
Shoaling
Swim level
Middle
Diet
Carnivore
Difficulty
Difficult
Breeding
Hard
Rarity
Rare
Family
Ambassidae
Origin
Native to the Malay Peninsula and parts of Sumatra and Borneo, in soft, acidic blackwater streams and peat swamps.

Overview

The threadfin glassfish is a small, semi-transparent glassfish that shoals loosely in the middle of a quiet blackwater tank. It is best left to experienced keepers.

Did you know

The threadfin glassfish takes its name from the males' trailing fin filaments. Males show them off in gentle displays to rivals and females.

Caring for the threadfin glassfish

Keep threadfin glassfish in a group of at least six to eight, in a tank of 16 gal (60 L) or more. Fill it with fine-leaved and floating plants under subdued lighting, and add leaf litter or botanicals for tannins. These shy, sensitive fish need a calm, mature tank.

Keep the water soft and acidic, at 73 to 81°F (23 to 27°C) and a pH of 5.0 to 7.0. It should be stable and clean, with gentle flow. The threadfin glassfish rarely accepts dry flake, so feed regular small live and frozen foods such as daphnia, cyclops, microworm and bloodworm.

It is peaceful but easily outcompeted, so keep it in a species tank or with tiny, gentle blackwater fish. Mature males grow long, blue-tipped filaments on the dorsal and anal fins, while females stay plain and lack the streamers. They are hard to breed.

Good to know

Gymnochanda filamentosa is a small glassfish in the family Ambassidae, the Asiatic glassfishes. Its transparent body is an adaptation for staying hidden in open, dimly lit water.

In the wild

The threadfin glassfish is native to the Malay Peninsula and parts of Sumatra and Borneo. It lives in soft, acidic, tea-colored blackwater streams and peat swamps with dim light and dense plants.

Weekly picks

Tank mates

The threadfin glassfish is a peaceful, shoaling 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 threadfin glassfish need?

A threadfin glassfish needs at least 16 gal (60 L). It spends most of its time in the middle.

What temperature and pH does a threadfin glassfish need?

A threadfin glassfish is comfortable at 73–81°F (23–27°C) with a pH of 5.0–7.0.

What does a threadfin glassfish eat?

A threadfin glassfish eats small live and frozen foods, such as daphnia, cyclops, microworm and bloodworm. It rarely accepts dry flake.

How big does a threadfin glassfish get?

An adult threadfin glassfish reaches about 1.6 in (4 cm).

Does a threadfin glassfish need a group?

Yes. A threadfin glassfish is a shoaling species and should be kept in a group, not singly.

How can you tell a male threadfin glassfish from a female?

Males grow long, blue-tipped filaments on the dorsal and anal fins as they mature. Females stay plain and lack the streamers.

Related species