jm1212 wrote:
first- you do not need to totally clean the tank every time you chang ethe water. 25% a week after your tank is cycled along with vaccuming the gravel with a siphon is enough.
your blue gourami was probably attacked by the other gourami in the tank. male gouramis are pretty aggressive towards one another, they will chase and fight with each other until one dies. blue gouramis can become bullies with fish that are smaller than they are, be careful and keep an eye on him with the other fish, they might get killed by either one of them.
I agree.
As for the neons.....Do you have a cover on your tank?
They may or may not have jumped, but a well covered tank would eliminate that possibilty.
Now....do you ever check your water values (ph, ammonia, nitrate, nitrite)? If your tank has only been running for a month....there's a possibility that your ammonia or nitrites are spiking and your neons are the "canaries in the coalmine." If they are, and they died overnight, the other fish might have eaten the corpses.
Jim1212 mentioned a 25% water change every week after the tank is cycled....do you know what he meant by "cycling." If not, we'll gladly explain it, or you can look it up, there are many threads on the subject.
Have you pulled up all of your tank decorations and sifted through the gravel? They also may still be in the tank. If that's the case, you want to remove the bodies- it's really not good to have decomposing fish in there.
Gouramis often do not get along well with each other....particularly different species. Your tank is large, so there was a possiblity that it would have worked out...but it would seem that perhaps it hasn't.
What kind of hiding spots do you have in your tank? If the water is too open, fish often feel exposed and get nervous....aggression sometimes results. Can you post a picture of your tank to give us a better idea?
In terms of the tank divider or separate tank, that's up to you. A divider would mean that you don't have to maintain two totally separate tanks. It would be a less expensive option. I, personally, don't always love the way dividers look (though sometimes it's done well)- other people like the look dividing their fish...it sort of makes one tank become two or three, without all the fuss of cleaning and water changing two tank....and the advantage of the more stable water parameters of a larger setup. On the other hand....I like the way small tanks with bettas look (not the little itty bitty betta box tanks, mind you- those are cruel- as I said before- I think that 2 or 3 gallons should be a minimum size.) Really, I think you should go to an aquarium store, look around and decide what you think looks best. Then you can either buy the products there or order them online (probably cheaper).
Now they have pellets, and veggies and a little cuttlebone. Happy turts!! 
