Will This Work For My Fish Tank?

So far I have:
1 - Dragon Goby (looks very healthy)
2 - Female Guppies (and about 20 fry, I am not worried about their survival, although about 4 of them are about 1.5 cm long now! and I've done nothing to aid their survival, other than lots of plants!)
and finally, I have just bought 3 gouramis (2 blue and 1 bright orange)

I have all of them in a 30 gal. and have turned it brackish, to help my little dragon goby survive (who I had bought along with 2 others, that died within the first week). To turn the water Brackish, I put 1 Tablespoon per 5 gal, I also saw that it should be 1-2 teaspoons per gal. but I only did the 1 tablespoon per 5 gal, so it would be too much to fast for my fish
I have a sand bottom. In the middle/front of the tank i have a natural looking smoothed-gravel bed (almond to chestnut sized, smooth rocks), fake vegetation on both sides, thicker on one side than the other. In the middle of the tank i have a tipped over lost-atlantis style pot, with some smooth gravel (3 rocks) inside. I have a pump for a 20-40gal tank, and the heater is only for a 10 gal (but thats all i could find, so am hoping it will do for now). The filter-pump is set up in the middle back of the tank. The heater is set up on the side with more dense vegetation.

Since I first set up the tank, and started with 7 guppys (3 males, 4 females), only 3 females survived the first month. After a while, when tank seemed stable and I thought all was good. I added 3 Dragon goby, I asked at the store if they had any special needs, so I could buy to accomodate them (really wanted them to live as they look so cool), and I was told no. As soon as I got home, I did some research, and found that they need brackish water and a heater. 2 Goby died [the two smaller ones died, the bigger one lived] and one female guppy within 3 days. Today I went and bought the heater and some Aquarium salt. My goby looks even happier than before, his tail finally fanned out (before it looked like a little hair hanging from his bum) and I see him eating and burrowing more than before. Along with this, I bought 3 Gouramis, 2 Blue and 1 Gold, asked the clerk if they would survive in brackish water, I again, was told yes ( and hope I wasnt lied to again!!!). I followed the directions on introducing them to their new home. Everything seems all well, all the fish seem very happy. the water is still pretty cloudy, and hasnt really settled at all, I just thought it was from the sand bottom and the filter pushing the sand around. I just want to know if this will work, any comments on my set up, anything more I should do, aside from the heater ( I know I need a bigger one). Please dont be mean...

tank has been set up since about late june. I have looked it up, and guppys will survive in brackish water, and are the recomended tank mates for Dragon Goby, says quite a few different websites. If Guppy and Gouramis are the same in this sense..... then all should work!! =)

Your first mistake was in not researching the goby before buying them. This could have prevented their death.
Although gouramis can tolerate some salt, I wouldn't recommend it simply because their natural habitat doesn't contain any..
The only time I would consider using salt with gouramis is if they had a disease, parasite, or fungus that heat wouldn't cure or get rid of.
And guppies can do okay in brackish water, but they do better in fresh water with a limited amount of salt.

Well, guppies and gouramis aren't the same.
If you aren't going to listen to advise from experienced aquarists on one thing, then just do what you think is best on anything else. They're your fish.

Neither the gouramis nor the guppies are brackish. The gouramis need to be removed to fresh water immediatly. The guppies are taking it a little better because they are pretty tough fish. But they will not live in brackish water for long either. You either need another tank, or to take some fish back to the store.

Gourami's are not brackish. You were lied to. They may tolerate a very small amount of salt, but not full brackish salinity. Guppies are the same as the Gourami. I'd quit asking that store for recommendations!

The cloudyness could well be a bacterial bloom, what are the water parameters? How long has it been set up? A very new tank that has not yet finished or only just finished the nitrogen cycle will go cloudy. Most fish won't survive the nitrogen cycle.

Which websites exactly say that? Gouramis will not tolerate brackish water.