what was wrong with my fish?

[Boricua]

My fish just died and I don't know why it was sick. I got a new tank last week and yesterday I bought a flame dwarf gourami, 3 skirt-tailed something or others, and 2 small catfish. The flame dwarf gourami looked fine at the store, but when I got home and settled him in he was acting strange. He wouldn't eat and was very inactive. I was searching online about gouramis and read a story about someone else's gourami acting strange and the owner resolving it by buying a companion for his fish. So today, I went out and bought another one at the same store (so both fish came out of the same tank) to see if companionship was my fish's problem. It wasn't. It started turning black today, starting from the top of its head and eventually spreading across half its body. It wouldn't eat and it would float there against a plant, gasping like it didn't have enough air. What was wrong with my fish? Why didn't my other gourami have the same problems, if I got both of them out of the same tank at the same store? is it possible whatever my fish had can be passed on to the rest of my fish? If so, how can I prevent that from happening? Why did my fish die?

 

[The-Wolf]

your tank has not cycled. adding lots of fish to an uncycled tank has caused an ammonia spike this inturn has poisioned your fish.
please read the many articles on this site reguarding cycling you tank.