You know, you are going to do what you want in spite of the advice.
You have fish such as the mollies, that nearly require a little salt with fish that are sensitive to salt, such as the corys and the loaches. Tetras don't particular like salt either. Corys can tolerate salt for short periods of time and it should be used in treatment of ich, but there is not much salt in the slow moving streams in South America where they are from. Hence for their long term health it should not be used.
Mollies and guppies in particular like hard alkaline water, though guppies readily adapt, mollies are prone to ich in soft water without salt constantly in the water. Guppies have even been found in similar brackish water as mollies as well as straight up fresh water so salt is not an issue for them.
Both mollies and guppies are live bearers, but I would doubt you'd keep many of the babies with the much larger gouramis in the tank, but the adults are large enough to survive.
About 24 percent of the Dwarf gouramis raised for aquarium trade in Singapore may carry dwarf gourami iridovirus. So it will pay you to know something about that disorder. They are also bubble nest builders and hence, like nice quite water, where as most of the loaches come from mountain streams and like fast moving water.
No consideration has been given to ph and water hardness favored by most of the fish. Both the live bearers like hard alkaline water and everyone else likes soft acid water. Fortunately, most of them are a hardy group and all tolerant of neutral ph and average hardness of water. . If you keep your ph neutral 7 and your water hardness near 12, not one will fail to live a full life span.
Do as you wish and subscribe to a good Tropical Fish Hobbyist magazine such as TFH. You can learn a lot about tanks based on what might actually be found in nature living in the same area with similar requirements.
Have fun with your tank.
OK reside
6- Molly's
4- platy
2- dwarf gouramis,...,.....,.............,..will get at same time
6- guppys
6 - Cory's
6- kuhlies loach
3 white skirt tetras
3 black skirts tetras
5 neon or cardnils
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