The Giant Gourami(Colisa fasciata) does only grow to 4" the true Giant Gourami(Osphronemus goramy) is a huge fish and will grow to an excess of 2ft easily in the aquarium. Kissing Gourami also grow to 10" in the aquarium. The Giant Gouram8(Colisa fasciata) *may* work out with your firemouths. Firemouths temperment seriously varies between individual fish, some people report theirs as model community tank members others repord them as being aggressive. But in either case I would definatly not keep Blood Parrots or Kissing Gourami with them in that size tank as the tank is just to small.