There are two distinct issues here.
First, tankmates. I am always glad when a member posts "proof" of what I (and others) advise, so I'm glad you started this thread. Gourami are sedate fish, and should not be combined with boisterous or active swimmers. All danio (along with barbs, and some of the tetra) are active; they love to swim fast and furious. And such fish are usually aggressive feeders too; which doesn't mean aggressive as in biting other fish, but when food is present these active fish will be sure they get what they want. Leaving the poor quiet gourami out. This is why rasbora, the quieter characins, etc. make better tankmates for gourami. There is not much you can do about the feeding habits of fish.
On the issue of the water hardness, can you give us the number for the GH? You can find this out from the municipal water supply people, they likely have a website. Without knowing the GH it is impossible to suggest if any adjustment should be made. I am going to suggest it likely does not, if your pH is 6.8, as usually the GH will not be too high, though there are always exceptions. I doubt this is an issue here, but I need the number to be sure. And we must deal with this before you start fiddling with RO water. GH, KH and pH are closely connected, and water chemistry is quite involved [you can read more in my article in the Freshwater Articles section on Water Hardness and pH...]; adding RO for instance is going to alter the GH, KH and pH, and it could be significant.
Last edited by Byron; 11-15-2012 at 04:14 PM..