# Sexing A Piranha



## A-ron (Jan 6, 2009)

Does anybody know how to sex a fish/piranha. Im sure you can surgically sex them but I dont want the hassle of that. I am strongly considering trying to breed black rhoms. I just recently bought a 550 gallon fish tank. My next step is to place 2 rhoms in the tank, but b4 i do that. I want to make sure that they are 100% sure male and female. I have already done quite a bit of research on the species and even have contacted several marine biologist on the subject! But I am just covering all bases, which is why I am also asking the question on here.

Thanks
Aaron


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## memento (Jun 3, 2009)

Most species are not sexual dimorph, so no way to be sure about the sex untill there is some pre-spawning activity...
S.rhombeus is one of those non-dimorph species unfortunately.


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## CLUSTER ONE (Aug 2, 2006)

CombiChrist said:


> Most species are not sexual dimorph, so no way to be sure about the sex untill there is some pre-spawning activity...
> S.rhombeus is one of those non-dimorph species unfortunately.


agree there is no distinctive difference thats consistant. Im sure theres some minor ones, but nothing thats works much mroe then 50%. If you are serious i would try a group of 4-6 adults above 8", but thats a pretty big price tag/food bill. I would seriously consider trying your luck with macs or some pygo. You may also want to start with breeding reds if you havnt already


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## Us And Them (Dec 4, 2008)

Great points made above. Also , I don't believe their have been any documented cases of Rhombeus breeding. Not to discourage you , but your more likely to have success with other Piranha in the Pygocentrus Genus such as Cariba and Piraya , if your looking to breed something other than Reds.


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## CLUSTER ONE (Aug 2, 2006)

Us And Them said:


> Great points made above. Also , I don't believe their have been any documented cases of Rhombeus breeding. Not to discourage you , but your more likely to have success with other Piranha in the Pygocentrus Genus such as Cariba and Piraya , if your looking to breed something other than Reds.


 You can vaguely say rhoms have been bred in captivity. It wasn't an aquarium, but rather a pond so its not really that much like an aquarium. Depending on the pond size it could be closer to the wild. Not positive but i think this happened at some abandoned florida park years ag


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## memento (Jun 3, 2009)

> _S. rhombeus_ reproduced in captivity in large public aquariums ie; Duisburg Zoo, Germany in 1977 (Schulte, 1988) and one time in U.S. native waters at a zoo park in Florida. ​ The reason why there haven't been more successful breeding in the home aquarium is the species are extremely aggressive with each other. Perhaps some pheromone is released in the water causing the aggressiveness to subside, but no real research has been done to see what the factors are to allow such spawning to take place. _S. rhombeus_ bred in captivity (public aquariums) require a huge volume of water.​.......
> The species is not sexually dimorphic. Some insight on the male and female differences were made but not conclusive for useful non-reproductive methods to determine sexuality during rest.​So what would he average hobbyist need to do in order to breed this species? Or is it even possible?​ ​When one considers the size of the aquariums that were successful, you are looking at having as a minimum 800g to over 1500g tanks. Or at the extreme, a large pool of water that is environmentally controlled. Could it be possible to breed this species in a smaller aquarium? As of this date, no hobbyist has reported such success. It might be possible one day to use a smaller tank (500g), but not likely. But until that day happens, let us stay within realism as much as possible. So, lets go by the assumption you have a monster tank of 800g's or more (even 800g is small but a good starting point). One of the key elements in such a tank would be a water drip method and wet/dry system for filtration. Water chemistry for this species is variable as its body morphology. So if you have one of the many different body shapes and localities of _S. rhombeus,_ it might be prudent to research the water your fish comes from, if you know. Otherwise here are some suggestions:​
> *Rio Xingu:* High water; Temperature 80ºF pH 6.7 6.9​
> *Rio Araguia: *pH 5.8-7.5 (6.5), 4-20 dH (8), 72-82°F (22-28°C)​
> ...


That's the only verfied info on breeding S.rhombeus, quoted from OPEFE.


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## marco (Jan 2, 2003)

you cant sex them at all. usualy the females are thicker than the males. but its hard to tell unless they are older and sexualy matured


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