Sudden gourami bullying

[Tenko]

I've had a male and female dwarf red gourami and a male dwarf neon gourami (his partner died a couple of weeks ago) in my tank for about 3 weeks now. They've all got along fine, until today.

My girlfriend noticed the dwarf red male having a nip at neon's tail this morning, but nothing since. A while ago I was having a look and in about 20 seconds the dwarf red female nipped neon's tail about 10 times. She followed him, nipped, followed, nipped etc.

I've had to isolate him in a breeding trap but his tail and top fin are damaged. I will do a water change and add that tapsafe stuff which is supposed to help prevent fin rot, but that's not treating the problem.

Does anyone know why this might be happening? Why they can suddenly turn on another fish? Is my only option to give him away? Any suggestions or advice?
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Just a thought, but yesterday I added 8 rosy tetras and 5 guppies. My tank is now stocked as per my sig. Could the influx of fish cause the aggression? If so would things improve when the gouramis get used to the new situation?

 

[fishdude]

well i would always advise not to ut two males together especially if in not a big enough tank. How big is your tank?

 

[Tenko]

100cm by 40cm by 50cm, 180 litres.?They,ve been fine for weeks until now.

 

[Morrgan]

This is not unusual when keeping several gouramis together. To me it sounds like the red ones have settled in and have started staking out a territory for themselves. This usually takes a few weeks, maybe months for some species. Perhaps the red ones feel like starting a family and want the neon one out of the way.

As a general rule it's best not to keep several gourami males in the same tank. Dwarf gouramis can be surprisingly nasty for their small size.

 

[Tenko]

I wish the lfs hadn't told me they were perfect community fish if that's not the case.

I had the neon in a breading trap but let him out today. The red gouramis were fine towards him. Swam by him and around him with no signs of aggression. I'm keeping an eye on them though. If they start attacking him I'll have to try and give them away.

 

[Tenko]

Hmmmm, all gouramis seem to be getting on fine again now. It's been about 14 hours since I let the neon back into the tank and no nipping has been spotted since.

 

[Morrgan]

Well, hope things work out for the best then. Just keep on watching them for a while. You have a pretty big tank, so hopefully that will be enough for two males.

 

[FanOFish]

I have found that when you have gouramis together you are going to have a lot of chasing and nipping. I had two dwarf gourmies and a large pearl gourami, the pearl would not leave the two smaller ones alone. I finally had enough and gave him away to a friend. Once the pearl gourami was removed one of the dwarf gouramis became the agressive one.

The good news is that they never seem to bother any fish other than each other and never seem to do any real damage...

That's my experience at least.