Swordtail maturation
 

Three months ago (June 4) our golden colored female sword had a batch of about
50 fry. They were kept in a 20 gallon tank, with a few guppy & molly fry.
About 6 weeks ago, I moved some to a 55 gal., and they've grown faster than the
others. My questions --

* None of them have developed swords on their tails yet (altho some are
visibly male w/ developed gondopodium). Will the swords develop later on the
males? At what age do the swords usually develop?

* Is it possible they aren't swordtails at all? I'm sure the female came from
an LFS tank that had similar males w/ swords in it, and the male sword in our
tank certainly was attentive to her. The fry's bodies seem long &
swordtail-like to me, but I'm wondering if maybe they're not swords at all and
actually platies (doesn't seem proper body type), or some type of orange-yellow
molly (is there such a fish?)

* There seems to be an extreme variation in body size among this group of 3
month old fish. The largest have grown to about 1.25", while some remain tiny
at about 1/4" (not much longer than new-born mollies). Will these runts grow?

* I'm wondering if the fry that were kept in the 20 gallon & which are smaller
than those in the 55 are permanently stunted, or if they will eventually catch
up? If not permanently stunted, any suggestions for encouraging proper growth
at this point?

Any insights would be most appreciated! -- Jim

"OldTownSta" wrote in message
...
Three months ago (June 4) our golden colored female sword had a batch
of about
50 fry. They were kept in a 20 gallon tank, with a few guppy & molly
fry.
About 6 weeks ago, I moved some to a 55 gal., and they've grown faster
than the
others. My questions --

* None of them have developed swords on their tails yet (altho some
are
visibly male w/ developed gondopodium). Will the swords develop later
on the
males? At what age do the swords usually develop?

If I recall correctly, the gonopodium is evident long before the
swordtail. The age of the tail depends on several factors, such as
growth rate, water temperature, diet and sex ratio.

* Is it possible they aren't swordtails at all? I'm sure the female
came from
an LFS tank that had similar males w/ swords in it, and the male sword
in our
tank certainly was attentive to her. The fry's bodies seem long &
swordtail-like to me, but I'm wondering if maybe they're not swords at
all and
actually platies (doesn't seem proper body type), or some type of
orange-yellow
molly (is there such a fish?)

Swords will cross with Platys but not with Mollys. Swordtail/Platy
hybrids (used to be called the salt & pepper Platy) will develop their
swordtail later (if at all, varies by fish).

* There seems to be an extreme variation in body size among this group
of 3
month old fish. The largest have grown to about 1.25", while some
remain tiny
at about 1/4" (not much longer than new-born mollies). Will these
runts grow?

Extreme variation in fry size typically indicates that their food source
was not incremented appropriately to their size. If for example, the
food available was in a size which was difficult to mouth, then you might
have 1/2 the fry manage it, and quickly outgrow those who didn't manage
it, making the size difference progressively worst, as they were now the
first to consume most of the food.

* I'm wondering if the fry that were kept in the 20 gallon & which are
smaller
than those in the 55 are permanently stunted, or if they will
eventually catch
up? If not permanently stunted, any suggestions for encouraging proper
growth
at this point?

Fry in a larger tank with a mixed community will typically grow much
faster than those in a fry-tank. It's a combination of greater food
diversity, better water and a more important neccsesity to grow fast (to
not be eaten by tank-mates ;~). The probability of a 'stunting' leaving
permanent effects, increases with their age. Once the juvenile growth
stage is passed, their growth rate typically naturally slows. You can
address stunting by diversifying the foods being given and including
frozen (ie: bloodworms, shrimp...) & live foods (ie: white worms, vinegar
worms, brine shrimp...). hth
--
www.NetMax.tk


Any insights would be most appreciated! -- Jim