Question bout swordtails

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That's interesting. I wonder why their behaviour is different to what we have here. I can understand wild caught fish behaving slightly differently but one would think the Asian bred stuff should act the same all around the world.
In the wild, most female livebearers hang out in large groups consisting of between 20 & 50 (but sometimes up to 100 or more) females. These groups have a pecking order with the biggest most dominant female ruling the group and she has a group of girlfriends who back her up. All the other females live in the group but are lower down the pecking order.

The groups of females move around rivers and waterways looking for food and places to hang out. As the groups move around a few males follow the group and try to breed with any females. The groups of males have a pecking order too and the biggest male will bully his smaller mates.

In the confines of an aquarium, the males will constantly harass the females and try to breed with them. This puts undue stress on the females and if there are too many males constantly pestering the females, the females can get sick and die prematurely.

In my opinion it is preferable to keep common livebearers like swordtails in single sex tanks (either male or female but not both sexes together). If you want a group of males and females then have 1 male and at least 6 females (preferably 10 or more females per male) so the harassment is spread out over more females.
So they're like teenagers.
If it get's crowded, it's like college. Bullies are at all levels, all off the time.

Hiding space and sufficient water volume.
I bred a lot of wild type swordtails, including helleri. If I had 3 to 5 males, I had no problem. 2 was a disaster. I kept them in large groups in large tanks, and had very little damaging aggression, but a lot of parading and showing off. I found with moving water and space, they were great.
But I saw no shoaling. They spread out and got along, but they didn't move together. I had busy tanks that ran for many years, but never saw a shoal. I did see a lot of interesting behaviour.
In natura, la maggior parte delle ovovivipari vive in grandi gruppi composti da 20 e 50 (ma a volte fino a 100 o più) femmine. Questi gruppi hanno un ordine gerarchico con la donna più grande e dominante che governa il gruppo e ha un gruppo di amiche che la sostengono. Tutte le altre femmine vivono nel gruppo ma sono più in basso nella gerarchia.

I gruppi di femmine si spostano lungo fiumi e corsi d'acqua in cerca di cibo e luoghi dove frequentarsi. Mentre i gruppi si spostano, alcuni maschi seguono il gruppo e cercano di riprodursi con eventuali femmine. Anche i gruppi di maschi hanno un ordine gerarchico e il maschio più grande farà il prepotente con i suoi compagni più piccoli.

All'interno dell'acquario, i maschi molestano costantemente le femmine e cercano di riprodursi con loro. Ciò sottopone le femmine a uno stress eccessivo e se ci sono troppi maschi che le infastidiscono costantemente, queste possono ammalarsi e morire prematuramente.

A mio parere è preferibile allevare gli ovovivipari comuni come gli spadaccini in vasche dello stesso sesso (maschi o femmine ma non entrambi i sessi insieme). Se vuoi un gruppo di maschi e femmine, allora disponi di 1 maschio e almeno 6 femmine (preferibilmente 10 o più femmine per maschio) in modo che le molestie siano distribuite su più femmine.
very interesting!
Many instead say that having a tank of only males is unnatural and causes too much stress in the males themselves.
I am a novice and one thing that stops me from having an aquarium of Platys or Guppies or Mollies or Swordtails is precisely the reproductive problem.
If you put the classic 1m 2 f you still see the females stressed and that give birth constantly until they die.
Furthermore the aquarium in a short time is full of fry.
Some say that the number reaches a certain point and regulates itself.
Do you think it is possible? What do you think about the stress speech for only males?
On one hand I would like some fry for my personal growth and to carry on the species in my tank, on the other I would not like to have too many to send the system into crisis and not let the fish live well.
I have always preferred single sex tanks for common livebearers just to stop the males harassing the females. If it comes down to horny males being stressed because they don't have any females to rape, or the females being stressed continuously until they die, I let the males stress so the females can live in piece.
I had the same concerns as Velvetgun. I finally got rid of all the guppies; except that 2 babies later turned up. Wouldn't you know, a male and female. I'm thinking of moving them inside, where I have a tank with a Hawaiian goby, who I believe will take care of any more fry. If the female gets too stressed I'll bring her back outside. Never a dull moment with these ridiculously tiny fish.
Some say that the number reaches a certain point and regulates itself.
That does happen. Especially, when the tank gets to cramped for all those fish. It's a natural thing to solve the overpopulation problem.
That does happen. Especially, when the tank gets to cramped for all those fish. It's a natural thing to solve the overpopulation problem.

I don't really like overstocking in any case. I don't think they live very well. What do you think about it ?
Maybe it's better to have a few males or really give up on these species
I used to keep several swordtail species in good sized tanks. None were domestics, but all were tank bred wild types. Juveniles shoaled, and as long as I had 3 or more males, they ignored each other. I'd get the odd dance off, and a few fights, but nothing fatal. I have (blurry) photos of 5 male montezumae swimming together looking like they're seeking a field to play sports on.
One of my swords, the large X mayae, were very tight shoalers.
When I was a kid, I thought swordtails were hyper aggressive. Then again, I tried to keep them in 10 and 20 gallon tanks. If you start with 40 gallons and up, you get a tank of beautiful, peaceful but competitive fish, in my experience.
Here's a possibly worthless thought. My swordtails were kept at 22c, and they thrived. They bred well and grew well, for generations.

I wonder if the Australian swordtail experience (good name for a band) is different because of higher temperatures affecting behaviour?
I don't know if higher temperatures affected their behaviour. The fish in the shop tanks were kept at 24-26C for most of the year (up to 30C in summer), and there were dozens of fish in each tank. The tanks were about 18-24 inches long so the fish were cramped and stressed. I never saw any weird behaviour in the shop tanks, presumably due to this.

The aggressive behaviour was at home and the water temperature fluctuated between 16-30C throughout the year. My tanks at home were 2, 3 and 4ft long, I had swordtails in various tanks over the years and they had the same attitude in each tank. The males were just bottoms. I did only keep 2 or 3 males (with 5-10 females) per tank and that might have been the cause of the problem. Eventually I just separated the sexes and had a tank with male livebearers (mollies, platies and swordtails) and a tank with females. If I wanted to breed them I put a female and male in another tank for a week and then separate them after that.

I wonder if the warmer water makes them more aggressive because it is breeding time.

Hey @emeraldking, do livebearers change behaviour in warmer or colder water?
Hey @emeraldking, do livebearers change behaviour in warmer or colder water?
It certainly can affect their behavior. But in a large school it won't be that visible.
is it worse in warm water or cold water?
are they more aggressive in warm water?
If we talk about breeding forms, the activity is more in warmer water. If we speak about wild specimens, it depends on the location of origin. If we speak about those coming from the mountain areas, they'll be more active in colder watrer than in warmer water. The ones coming from lower areas, will be more active in waremer water than in colder water. "Active" can also mean aggressive in this case.

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