size differences of mature fish... normally an indication of sex, or other reasons???

[Magnum Man]

So, I have 2 "Flying Foxes" purchased from the local pet store, at the same time, about 4 years ago, one of the 1st fish I bought, back when I restarted my tanks, after a 25 year break in the hobby... honestly, they were mostly bought as "canary's" on a newly set up tank... totally an uninteresting fish...
but at time of purchase, one was slightly bigger, and they have been in a 55 gallon tank, since purchased... now, 4 years later, one is twice the size of the other... both have been able to eat what they want ( within reason ), so I don't think there would be significant environmental reasons for the size difference... and they have never shown any sexual interest...

I think on some fish the male is bigger, but seems most often the female is the larger fish... I don't think this species is easy to sex... at least for me...

they used to chase around more... the bigger fish the dominant, but after several years they have become more tolerant, of each other, both sitting on the same coffeefola this morning for a few minutes...

thoughts???

 

[GaryE]

It can be sex, with some species having larger males, most have larger females. It can be juvenile diet, or other early life events. It can be the kind of variation we have, with height, bone structure, etc.
Back in the no water change era, I bred generations of one inch long X variatus platys. When I gave up on the balanced aquarium mythology and started intervening about water quality, the first weekly water change generation was more than double that size - just like wilds.
What happens if they didn't come from the same farm, or from different rearing conditions?
When I started teaching, for many years I was always the tallest person in the classroom. As people improved their nutrition, vaccinated against childhood diseases, had better healthcare etc, by my last year, my 2 classes had three Grade 9, 14 year old boys taller than me. That had become a common pattern, and I'm not shrinking yet. I can now easily buy shoes since there are more people my size! 20 years ago, that was a problem.
It's the same things at play with fish. Hormones (they can hormonally stunt each other), DNA, conditions of life...

 

[fishorama]

It could also be a matter of a dominant fish & a "lesser" submissive 1, especially if they are the same gender. They may not fight, but often the larger fish of either sex gets "first dibs" on more food, always. Sort of natural stunting?

Other than size, do you see differences in body shape? Females often have rounder, sometime whiter or greenish, "tummies"; males may be slightly more colorful & slimmer. They should both be adult or almost by now even for slow growing fish.

@GaryE I used to be fairly tall for my younger age & even female gender. I quit growing early & others didn't. I never could see over crowds at concerts ;(

Now I have lost some height. A friend made a tank stand for me & my dimensions (height & reach). 15 years later I can't reach the back bottom corner even with 2 or 3 inches of substrate, eek! I still pretend I'm the same size.

I doubt that happens to fish, lol. Gravity doesn't have the same effect on length. But very old fish I've had do tend toward bent backs.

Magnum, are you seeing that yet? I'd guess not, IME with other species, often small fish = shorter lives, but certainly not always. Since you foxes can grow 5-6 inches they may not be at their "full possible size" yet. Some say fish never stop slowly growing but I'm not sure I buy that.

 

[Magnum Man]

I guess twice the size, was an eggageration, I'd at in reality, the smaller is close to 4 inches, and the bigger closer to 6 inches... it would have been nice to get a picture of the 2 of them on the same plant... I'll get a couple pictures today or tomorrow...

 

[Back in the fold]

Sounds to me like they just got used to the routine on the yard and got nothing to prove anymore .

 

[Magnum Man]

smallest...

biggest...

 

[fishorama]

It's often hard to guesstimate fish size. My husband is a great 1 for Irish "blarney".

Not to be too picky, but both don't seem to be the species I think of as "flying foxes". Maybe just a camera/lighting thing? They seem dark to me...still cute!

 

[Magnum Man]

it's just before lights out, so I'll try again tomorrow...