I will add a couple things to what Demeter32 has mentioned (and I fully agree with those items).
First, the knifefish is not going to be healthy/happy in this tank. Looking ahead, it will attain 24 inches and being inflexible (thee spine) needs a tank at least 2 feet width (front to back) and no less than 6 feet in length. If this is not going to bee possible, it would be best to re-home the fish now, as the tank size affects its growth continually. There are other issues too. Light...this fish does not do well under overhead lighting; it should have a dark tank, which can be achieved with floating plants and dimmer lighting, or obviously no tank light but that is not too practical. Environment...this fish must have places to "hide" full body. It must not have active tankmates as these will stress it terribly; sedate fish work well. Pictus cats (another shoaling fish) are far too active, as are danios, to name a couple here.
The gourami appear to be Trichopodus trichopterus, a species that has been developed into several "artificial" varieties, such as blue, gold, cosby, 3-spot, marble, opaline. All are identical in behaviours/temperament/requirements as they are the same natural species. It is one of the most aggressive of the small/medium sized gourami, and females as well as males have been known to "seem" peaceful for months then suddenly turn on anything and everything.
Leaf fish...this needs a heavily planted tank as it is an ambush predator. Out in the open it is stressed, severely. It would be best on its own in a suitable tank. Not a community fish.
Tiretrack eel...another predator that will eat smaller fish, and grow to over 2 feet. Not a community fish.
Disease and ich were mentioned...all of the above issues plus those raised by Demeter cause stress, severe stress. Stress is the direct cause of 95% of fish disease, and always of ich. With these issues present, the fish are never going to be relaxed and healthy, that we can guarantee. I do not mean to be didactic, but the truth must be made clear for the sake of the fish.
Byron.