wow! i guess i'm lucky! i have had my gorgeous betta in with both gouramis, platies and cories and they all get along fine! just about a year together and no real problem. he does like baby mickey mouse platies though... :evil_lol:
Yeah, you need a much bigger tank. Going by the 1" rule, you're overstocked, but a lot of your fish need territories and space to avoid aggression problems. Your MBuna needs to find its way back to the fish store or to another tank. It will grow and it WILL kill all of the fish in the tank.
Sadly I am too late. I had planned on taking him back to the pet store tonight when I got home from work and letting the sales clerk know I was very unhappy and why. However, my wife just called and said that he is laying on his side at the top of the water barely moving. will see what happened when I get home, but no other fish are showing any signs of distress so I think he got beat up and probably killed. He wasn't showing any signs of abnormal behavior this AM when I left. Sad.
I'm only going to say that bettas and gouramis often get along just fine depending on individual temperament. But you really have to know what you're doing, and I wouldn't ever recommend so many in one tank.
I would also add that danios are nippy and annoying to bettas.
I would just leave well enough alone.
My best advice? Get the betta his or her own five gallon tank. Use very gentle filtration and some peat or indian almond leaves. Plant it heavily. Happiest bettas ever.