Agree, pin down the number for the GH with your water authority. As for the Paradise Fish, I would advise against this given the fish already present. Here is my profile of the species.
Macropodus opercularis
Family: Osphronemidae, Subfamily Macropodusinae
Origin and Habitat: An extensive range through parts of southeastern Asia to China, Korea and Japan. Found in any type of lowland habitat including river backwaters, small streams, ditches, ponds and paddy fields. Shows a preference for still and even stagnant waters. Most available fish will be commercially raised.
Compatibility/Temperament: Not a good community fish for the average aquarium. Smaller fish will be eaten, fins will be nipped, and any similar-looking fish will be attacked. Very aggressive with its own, males in breeding form will often kill rivals; females are less aggressive. Best kept as a pair on its own.
Diet: Omnivorous. They should be able to accept all types of food provided.
Size Normally around 3.5 inches, some males may attain 4 inches.
Minimum Tank Suggestion: 30 inches in length (approximately 25-29 gallons).
Water parameters Very adaptable. Soft to moderately hard (up to 30 dGH), acidic to basic (pH 6 to 8) water, temperature 16-27C/61-80F. Displays its best colouration around 21-24C/70-75F.
Description
While it is quite a beautiful fish, its former popularity has waned now that there are so many other colourful gourami available that are more suitable for community aquaria.
The aquarium should be well planted with subdued lighting, partly achieved by floating plants; minimal flow from the filter suits this fish which prefers very still waters. In common with all the species in the suborder Anabantoidei, this fish possesses an auxiliary breathing organ called the labyrinth, named because of the maze-like arrangement of passages that allow the fish to extract oxygen from air taken in at the surface. The fish must use this accessory method, and it allows the fish to live in oxygen-poor muddy waters. To accommodate this, the aquarium must be kept covered to maintain warm moist air above the surface.
Sexing is easy as males are more colorful and have longer fin extensions compared to the females. This species is a bubblenest spawner. The male builds the bubblenest and entices the female under it. Following the common anabantid embrace, the eggs are expelled and fertilized and then picked up and spat into the nest by the male who then guards the nest. The female must be removed to protect her from the male. He should be removed once the fry reach free-swimming stage before he thinks of eating them.
This is probably the first ornamental fish aside from the goldfish to have been imported to Europe; to France in 1869 and Germany in 1876 [Fishbase].
This fish was first described and named Labrus opercularis in 1758 by Carl Linnaeus in his monumental Systema Naturae, the classification of all then-known species of life on earth that has developed into our present-day binomial nomenclature system. The genus name Labrus means furious, and presently contains four species of marine wrasses, all other former species having been moved elsewhere. The subject species was moved to the genus Macropodus [Lacepede, 1801], the writer assumes by Liem (1963) who also proposed changing the subfamily from Macropodusinae to Macropodinae [accepted by the Integrated Taxonomic Information System]. The taxonomy of the family Osphronemidae is in review.
In 1790, M.E. Bloch described the fish Chaetodon chinensis; this was determined to be the same species by Paepke (1990) and the name is now an (invalid) synonym.
References:
Liem, K.F. (1963), "The comparative osteology and phylogeny of the Anabantoidei (Teleostei, Pisces)," Illinois Biological Monographs No. 30.
Paepke, M.E. (1990), "Zur Synonymie von Macropodus chinensis (Bloch, 1790) und M. opercularis (Linne, 1758) und zur rehabilitation von M. ocellatus Cantor, 1842 (Pisces, Belontiidae)," Mitteilungen aus dem Zoologischen Museum in Berlin, v. 66 (no. 1), pp. 73-78.
Sorry... But still, look up on their page.
