Trichogaster trichopterus sumatranus Ladiges, 1933
COMMON NAME: Blue gourami.
DESCRIPTION: A subspecies with a powder blue background colour; as far as can be determined, this is a wild colour mutation. First imported in 1933, it quickly became popular as an aquarium fish. Today it is kept more commonly than most other forms of the species. There are hardly any marks at all on this fish, except for the two body spots, but even these look more or less washed out in adult specimens.
BREEDING FORMS of trichogaster trichopterus.
Several specially bred color forms of T. trichopterys have come into the aquarium trade during the last few decades. In most cases it is not possible to determine whether a particular color form was bred out of the original described form or from the blue subspecies. T. t, sumatranus
These forms should just be given common names and no attempts to taxonomically classify them, as has done in much of the aquarium literature, should be attempted. Designations such as var. variety) or forma (form) should not be used
for such breeding forms, since their origins or derivations are really unknown. The best known of the breeding forms are the gold gourami and the silver gourami.
GOLD GOURAMI
The gold gourami has a golden yellow background colour with either black or reddish brown eyes. Most specimens show a clearly conspicuous marble pattern. It is usually assumed that this breeding form was developed from a xanthistic (yellow-colored) mutation of the originally described form.
SILVER GOURAMI
The silver gourami has a silver background colour. There are some individuals that have a clear marbled pattern and others in which this pattern is only weakly apparent. Nothing is known about the origin of the
first specimens. In contrast to the gold gourami, the silver gourami has not had much distribution in the aquarium trade.
COSBY, OR MARBLED, GOURAMI
The Cosby gourami, or marbled gourami, was probably developed in the United States. The original specimens seem to have been Trichogaster tricbopterus
sumatranus, When they first colour up the
have a few dark blue spots on a powdery light blue background. As
replaced by a dark marbled pattern. These striking marked fish are very popular in the aquarium hobby.
This color form has been designated with all kinds of pseudo-scientific names, such as Trichogaster cosby, "Trichogaster sumatranus, var. cosby," or Trichogaster
sumatranus forma cosby."
Labyrinth Fish Pinter (1984) p86
Picture https://www.thesprucepets.com/blue-gourami-1381023
