Aggressive Female Koi Swordtail, what do I do?

[Ruby Red]

Hi all, I'm brand new to this forum so I do apologise if this is the wrong category or the one millionth and one time you've had to answer this question, but I've got an issue regarding a female Koi Swordtail, recently I purchased 4 swordtails, they are 3 different species, 2 are the same, but seem to get along fine, and 3 of them have been absolutely perfect, but one, the Koi Swordtail, seems to be harassing my Pearl Gourami and Pentazona Barbs, mostly nipping at them or chasing them around, but I've got no idea why - I'd like to know what I should do about this, should I remove the Koi Swordtail and find a replacement from another species to keep the male happy? Do I keep her in and see how it goes? Any advice would be greatly appreciated, thank you!

 

[Ichthys]

(Swordtails are all the same species).
I wouldn’t keep Swordtails with Pearl Gouramies. The gouramies are timid fish that like a quiet life and Swordtails are very active and can be boisterous, which will stress the gouramies.
Also Swordtails need hard water and the gouramies do better in soft.

 

[Ruby Red]

(Swordtails are all the same species).
I wouldn’t keep Swordtails with Pearl Gouramies. The gouramies are timid fish that like a quiet life and Swordtails are very active and can be boisterous, which will stress the gouramies.
Also Swordtails need hard water and the gouramies do better in soft.

Sorry I meant type, not species, and would've been great if I knew that sooner, since I asked one of the people at the shop I bought them from and they said they would be fine with them, I'd kept swordtails with Golden Gouramis just fine in the past so assumed the same, at the moment they all seem fine, what exact levels of PH or whatever do they require to be at their best?

 

[Ichthys]

This is from a Practical Fishkeeping article…

“Aim for a pH of between 7.0 and 8.0, with a hardness value between 10 and 20° DH, though they seem to fare better at the higher end. Go for a temperature between 22-28°C/72-82°F.”

Great fish: Swordtails

www.practicalfishkeeping.co.uk

This is also a good one…

Xiphophorus hellerii – Green Swordtail (Xiphophorus helleri, Xiphophorus guntheri) — Seriously Fish

www.seriouslyfish.com

Just to clarify, there are several different species of Swordtail but the domestic varieties are the same (they’re actually hybrids between Swords and Platies).