Dwarf Gourami chasing and nipping new fish?

[PeaceLove]

I have a 35 gallon hex tank, with 5 zebra danios, 3 cory cats, and 1 dwarf gourami (one of them died from an unknown cause). I recently (2 days ago) bought 3 platies and another dwarf gourami to pair up the other one, because I noticed it was hiding a lot. When I put in the new fish, I noticed the older dwarf gourami was nipping and chasing them. The older dwarf gourami is moderately larger than the new one, and thinking about that at the store, I asked to get the largest one. This has not changed the chasing factor. The chasing and nipping is still happening, will it ever end?

Extra details:

Both of the gourami's are males, and I thought this would be ok becaue the previous ones were both males, and it worked out fine.

One is a flame gourami (the older, bigger, and aggressive one)
and one is a neon blue gourami

could this be why? Or is the gourami just defending its territory? If so, why hasn't it stopped? Oh and I am not interested in getting a tank divider, I just want all my fish to live together in harmony

Thanks.

 

[Frawgg]

Instead of getting a tank divider, I suggest rearranging the tank.
This way, your gourami will think that he's in a new tank, and so will all of your other fish, therefore, they will most likely not attack eachother. If this don't work, though, for some reason, you may want to invest in a bigger tank, or, a tank divider.