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Discussion Starter · #1 ·
I have four of each which are roughly 2.5" each.

I have yet to see any breeding or signs of breeding. The tank is fairly peaceful and houses a few other metriaclima species of similar size. I do 25% water changes once [sometimes twice] a week.

Could it be possible that I have all male labs and all male rusties? I thought rusties and labs are typically pretty prolific and breed at a fairly small size. I have had them in the tank for about 2 months... am I just being impatient?

:-?
 

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I have had them in the tank for about 2 months... am I just being impatient?
Most likely yes..

The chance that you picked 8 males or 8 females is HIGHLY unlikely (someone superior to me will chime in with a percentage), there's a possibility that at 2.5" they are still not sexually mature, or just not comfortable with their surroundings. What are the tank dimensions?
 

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Discussion Starter · #5 ·
thats a pretty cool table, nonetheless, 0.39% is not zero. Highly unlikely to have all males, but not impossible right

Dont know how patient i can be
 

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I can't take credit for the table.

Although, looking at it again, I'd say the likelihood of non-breeding being caused by all fish of one sex would have to be much closer to zero, since if one of your 16 fish was a different sex than the other, that one fish would be breeding with one of the other 15. As maternal mouthbrooders, "caged" mbuna aren't that picky about which species they breed with!

Id' chalk it up to 'not enough time' if they are otherwise behaving normally.

kevin
 

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I find newborn fry spawn sooner (six months) than juveniles brought home and introduced to a new tank (eight to twelve months). Don't know why.

And don't forget, when I say I've had labs hold at 1.5" it was one individual out of a clutch of 20 fry I was raising. The other 18 did not spawn at 1.5".
 

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Discussion Starter · #8 ·
ridley25 said:
bmweiler09 said:
The chance that you picked 8 males or 8 females is HIGHLY unlikely (someone superior to me will chime in with a percentage)
In each case, the chance of picking 8 fish of the same sex is 0.39%

http://www.africanfish.net/blogBinomial ... nomialDist

kevin
I'm bringing this thread back from the dead. Is this probability correct or is it really a 3.125% chance

8x8 is 64 possible outcomes

Only 2 of the 64 would be the same sex

M M M M M M M M

F F F F F F F F

2/64

Also, if you take the individual groups of four you would be talking a 12.5% chance of having all of the same sex

2/16

M M M M

F F F F
 

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Limpert - in short, no. Yes, there are 64 possible combinations of male vs. female, but think of it this way:

First fish is M or F. 2 combinations.
Given that first fish is M, second fish can be M or F.
Same for first fish being F. We're up to 4.
Third fish: MM_, MF_, FM_, FF_. That's 8, since _ can be M or F.

So really there are 2^8 possible combinations, only one of which is all male.

With each species, it's 2^4, which is indeed 16, and thus you're correct that there's a 12.5% chance for him to have no breeding possibilities with each one.

Note: 2^8 = 16x16, which might help the first part make more sense, given the 2nd part.
 

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Not to be argumentative, but in a practical sense the odds of getting, say, 8 male fish from the same tank of juvies would be even less than 0.39% if you started out with a tank containing a perfect 50/50 split... because after you pick the first one you are no longer picking from a tank where the odds are 50/50 of getting a fish of the same gender as the one(s) you picked before. (Anyone remember the stat formula for that?) All this of course is predicated by the starting m:f numbers in the tank you're picking from. And to complicate things, with a species where only one or two males will colour up at a time in the presence of many others the customers before you may have depleted the tank of males. Or may have depleted it of females if they were trying to get breeding groups and had an eye for sorting out the genders early... Many uncontrollable variables - let's just say the odds of getting 8 fish that are all male by accident would normally be somewhere in the very low to really low range.
 
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