# how to tell the sex of a mature diamond rhom



## transam97 (Mar 25, 2004)

I was wondering if anyone had any info on telling male from female rhoms. I recently got two large daimond rhoms one measures 10 1/4 the other 11"+ the small one has a higher back and is more round than the larger one. here is the info I have on them they were netted from the amazon 2 weeks ago they were caught in the same cast so they were together at the time they were caught. I know Im taking a long shot here and obviously hoping for the best but could this possibly be a pair??? just like to know what you guys think

the pics suck they were taken with a camera phone I will post better pics after I give my wife her new canon dslr camera for christmas









This is the 10" 1/4







the 11"+


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## notoriouslyKEN (Jul 31, 2003)

As far as I know, no piranhas are sexually dimorphic. You will not be able to tell gender based upon appearance. However, according to statistics, you do have a 25% chance that you have a male and female fish ((1/2)^2).


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## transam97 (Mar 25, 2004)

thought it would be a 33.3% chance lol 2


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## Piranha_man (Jan 29, 2005)

Does it stand or sit when it pees?

Just kidding...
Yeah, ya can't tell by looking at them.


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## transam97 (Mar 25, 2004)

I figured that their is no way of telling guess I will just have to wait and see if they spawn... That would be amazing!!! right now I have them sharing a tank with a egg create divider so they can see each other clearly. only months or years will tell either way these are 2 of the best looking diamonds I have ever seen and their massive. if you couldnt tell Im super stoked to have these two.


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## notoriouslyKEN (Jul 31, 2003)

transam97 said:


> I figured that their is no way of telling guess I will just have to wait and see if they spawn... That would be amazing!!! right now I have them sharing a tank with a egg create divider so they can see each other clearly. only months or years will tell either way these are 2 of the best looking diamonds I have ever seen and their massive. if you couldnt tell Im super stoked to have these two.


Those are beautiful fish. I hope you have them in a good size tank and that your divider is *VERY* secure. Piranhas have been known to knock down a divider before to _check out_ their neighbor, which can often lead to casualties.


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## transam97 (Mar 25, 2004)

oh yeah the divider is secure bottom is anchored in4" of gravel and the top tied off to hooks I mounted on the outside of the tank it should not go anywhere

but if you have 2 piranha the only combos are 2 males or 2 females or 1 male and 1 female thus 33.3% chance for a male female combo


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## CLUSTER ONE (Aug 2, 2006)

transam97 said:


> oh yeah the divider is secure bottom is anchored in4" of gravel and the top tied off to hooks I mounted on the outside of the tank it should not go anywhere
> 
> but if you have 2 piranha the only combos are 2 males or 2 females or 1 male and 1 female thus 33.3% chance for a male female combo


Wrong, You can have MF,FM,MM,FF Its a 50% chance at a pair of male females. Fish one female fish 2 male is different then fish 1 male fish 2 female.

Either way there are no definite ways of sexing meaning nothing that a concrete indicator of the sex.


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## transam97 (Mar 25, 2004)

sean-820 said:


> oh yeah the divider is secure bottom is anchored in4" of gravel and the top tied off to hooks I mounted on the outside of the tank it should not go anywhere
> 
> but if you have 2 piranha the only combos are 2 males or 2 females or 1 male and 1 female thus 33.3% chance for a male female combo


Wrong, You can have MF,FM,MM,FF Its a 50% chance at a pair of male females. Fish one female fish 2 male is different then fish 1 male fish 2 female.

Either way there are no definite ways of sexing meaning nothing that a concrete indicator of the sex.
[/quote]

correct I did not count MF and FM as two of 4 because they are the same Im sticking with 33.3%


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## TJcali (Mar 27, 2009)

so are you going to leave them together?


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## transam97 (Mar 25, 2004)

yes in the divided tank


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## notoriouslyKEN (Jul 31, 2003)

Oops...I did my math wrong and was saying you have a 25% chance of guessing the sex right on both fish. I forgot if you guessed wrong on both fish, you could still have a male/female pair.


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## CLUSTER ONE (Aug 2, 2006)

notoriouslyKEN said:


> Oops...I did my math wrong and was saying you have a 25% chance of guessing the sex right on both fish. I forgot if you guessed wrong on both fish, you could still have a male/female pair.


The odds are 25% at having the pair you guessed, hovever theres another 25% chance of a pair thats opposite to what you guessed so thats 50%


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## Us And Them (Dec 4, 2008)

Hey Trans ,

IMO , I Believe its gonna take more than just 2 sexually mature S. Rhombeus to swing this one.
Alot of it has to do with the Water , Temperature , Diet , Time of Year .

You will need something along the lines of 1000 Gallons , if you want your Rhombeus to have sufficient space.


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## lo4life (Aug 12, 2008)

Wouldnt get ur hopes up. But nice fish. I would do this but they would chew right thru that egg crate and kill eachother. Thats just the luck i have lol

Even if you do have a MF pair its unlikely that they will breed. I mean with the egg crate in there they cant breed like they do in the wild. Keep us updated though.. GL


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## CLUSTER ONE (Aug 2, 2006)

Either way assuming you even have a pair, its doubtful that they will breed and too large of a risk imo. Unless its in a huge tank, i wouldnt try it as most peoples tanks arnt large enough for the rhoms to aviod eachothers aggression.


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## transam97 (Mar 25, 2004)

oh I dont have my hopes up I just think it could be a tiny possibility thats all


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## Grosse Gurke (Jan 3, 2003)

If you guys are assuming there are an equal number of males and females...I think the odds are better then 50% you will get a male/female pair. No matter what the sex of the first fish is.....after he is removed from the sample&#8230;.there is a greater number of the opposite sex left to choose from...so you have a greater then 50% chance the next fish will be a different sex then the first. At least that is how my brain works.

If you have 4 fish...two male and two female. If you pick a male fish first....you are left to choose between 1 male and 2 females....odds are you will pick a female.


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## Johnny_Zanni (Nov 8, 2009)

thats true GG and even if you were to pick another male then the odds of a female would go up again


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## notoriouslyKEN (Jul 31, 2003)

yea, but these fish were pulled from the wild and there are thousands in the populations. So if you remove one male, your chance of pulling a female is only increased by a tiny percentage, like .001%


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## lo4life (Aug 12, 2008)

I highly doubt if there would be thousands in a particular space. Last I checked Rhoms dont normally shoal.


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## CLUSTER ONE (Aug 2, 2006)

notoriouslyKEN said:


> yea, but these fish were pulled from the wild and there are thousands in the populations. So if you remove one male, your chance of pulling a female is only increased by a tiny percentage, like .001%


I agree with this variable, but the difference is negligible so it doesnt really matter. With this, you have to also assume the male to female ratio is exactly 1:1


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## notoriouslyKEN (Jul 31, 2003)

lo4life said:


> I highly doubt if there would be thousands in a particular space. Last I checked Rhoms dont normally shoal.


No, but you are removing the fish from the population. I am sure there are thousands of rhoms in the wild.


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## transam97 (Mar 25, 2004)

WOW!! this has been looked into a bit to much its a 33.3% chance in common probability MM MF FF(FM not included as it is the same as MF) it has to be I of the 3 combos.


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## CLUSTER ONE (Aug 2, 2006)

transam97 said:


> WOW!! this has been looked into a bit to much its a 33.3% chance in common probability MM MF FF(FM not included as it is the same as MF) it has to be I of the 3 combos.


 It is one of 4 combos they are not the mf, fm is not the same and you cant just group them together. There are 4 possibilities regardless if they are the same. You cant make a group with two ways to acheive that outcome without adding their probabiliites together.

MM, *MF, FF,* FM
4 possibilities
Even though 2 of them have the same outcome, you cant say there the same as the same thing was acheived in a different way. Thats the same as saying MM, FF are the same since its not a pair. Following through your logic:

MM, MF, FF, FM--> MM=FF (non pair percent) and MF=FM (Pair percent)
Since after following through with your logic, there are 2 possibilities, its a 50/50 change and once again i am right.


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## Piranha_man (Jan 29, 2005)

Is this thread really still going?

Such a simple answer!

"No."


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## Buckman (Jan 10, 2007)

how do you sex them, you ask? my answer, you don't.

but you could always cut them open and see what they are, totally defeating the purpose of this entire thread.


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## Piranha_man (Jan 29, 2005)

Hey, I've got an idea, let's turn this into a huge thread about the fact that you can't identify the gender of a piranha!









Who's with me?


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## RedneckR0nin (Nov 5, 2008)

I can sex a Rhom but the only problem is I am the only one in the world that can do so. I am booked solid into the new year to come and stare at fish genitals. But I can probably fit you in around March or so. It costs 10K and is non refundable if I am wrong!


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## jp80911 (Apr 3, 2008)

I charge only half what RnR charges


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## assclown (Dec 12, 2005)

my head hurts after reading this post...........


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## AmazonAddict (Jan 20, 2009)

The answer is no. You should get a 50,000 gallon tank and like a dozen Rhoms. Then you might get a pair.


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## Piranha_man (Jan 29, 2005)

So hey, guess what.
Ya can't ID the gender of a rhom.

Can you believe it?

Input?

Comments?


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## primetime3wise (Sep 28, 2003)

sean is right about the probabilities...some pretty sad statistics fail in this thread.....


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## Buckman (Jan 10, 2007)

i'll give you 10 bucks to sex your rhoms.


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