Opaline Gourami And Blue Neon Platy

For what it's worth, I thought I'd document this experience in case it's interesting or helpful to anyone else.

I have a beautiful, healthy opaline gourami -- I think, though not positive, a female -- that hasn't given me any problems in a community tank with tetras, red platys, Cory cats, and loaches. She's been peaceful and fun to watch.

However, a few days ago I introduced three "neon blue" platys to the tank, and my gourami immediately became aggressive toward all of them. Every time one came into her line of sight, she would draw a bead, then charge and chase him around the tank. Only the blue platys (not my reds) brought out this trait and seemed to drive her to distraction.

My theory -- and that of the LFS guy -- is that their coloration is so similar (sort of shimmery lavender blue) that my gourami thought the platys were fellow members of her own species, and of course gouramis are aggressive toward other gouramis. I didn't think fish could mistake other species for their own, but there is no other explanation.

I've isolated Ms Gourami in a net breeder for now and will be re-homing her to a new tank. LFS guy said a week in the penalty box night teach her a lesson and make her less aggressive if I let her back into the existing tank, but I'm skeptical. Thoughts on this?

 

That might work but what I would do is re-arrange the tank and then put her back in. She may feel she has to re-establish a territory and leave the platies alone. If that doesn't work, then I would separate her to a different tank. What size tank are they all in?

 

Thanks. They were all in a 40 gallon. Wasn't going to rearrange, because my decor and plants are arranged in a very deliberate way. I've moved her to a new 15 gallon column tank and she seems healthy and happy. I recognize she may in time outgrow such a tank.

 

What else is in the 15g? Might have been better to move the platys there and keep the gourami in the 40g.

 

I have a paradise gourami with a fantail goldfish, and had them separate for a few weeks to let some plants grow that the goldfish wouldn't leave alone. so when I re-introduced the fantail the gourami went after it and was being aggressive I watched for a while to see if it would stop but it didn't so I took the gourami out for a while to let it claim the territory, and waited about 30 mins to 1 hour and re-introduced the gourami and everything has been fine since, so I don't think you would need a week... but the longer the better I guess. but it was amazing to see the difference in behaviour. so I basically learned to always add aggressive fish last cos they will fee like they are in the other fishes territory instead of feeling like they are being invaded