"Rick" wrote in message
...

"OldTownSta" wrote in message
...
What sort of density is acceptable for raising baby fish without
stunting
their
growth?

I'm using a 55 gal. tank for babies. This seemed sort of ok for 48
baby
guppies & a few baby zebras a couple weeks back. --- Decades ago I
heard
somewhere that you could support 1" of fish per gallon (by which
figuring
I
plan to be able to keep a ten foot sturgeon in a 125 gal tank, with
space
left
over for a couple cories...)

However, now I've got 40 baby mollies to put somewhere, and I'm
starting
to
wonder if trying to raise about 100 babies in 55 gal isn't pushing it
a
bit.
It's not as dense as lots of tanks in fish stores, but I'd like these
little
critters to be able to reach some sort of semi-adult size. Is that
possible
in this size tank?

And what the heck do I do with these fish when/if they grow to a more
or
less
adult size?

Thanks -- Jim


I have loads of various fry with about 50 Kribs in a 20 g tank. They do
o.k
for several months at which time I normally sell them all to a LFS. As
the
fry grow you will notice some getting much larger than others and that
is
usually the time or at least it is the time I try to separate them. A
few
bigger fry will eat a lot of the food leaving the smaller guys without
too
much. With a 55 g tank you should have no problem. The 1" fish per
gallon is
a basic rule of thumb and as you point out you could keep 10 x 1" fish
in a
10 g tank but you couldn't keep one 10 " fish. More important is the
surface
area of the tank.

Rick

I agree with Rick. Your most important parameters are your filtration,
rate of water changes & feeding (size/quantity appropriate - variety -
often). Fish-loading needs to respect swimming space (which fry don't
need much of), territorial requirements (not applicable until the fry are
much larger), mechanical filtration (which is very modest with fry),
biological filtration (which is one of your early constraints) and water
quality (probably the most critical).

While fry do not produce a lot of waste, they are much more sensitive to
it, so over-filtering (x2 tank volume) with low flow systems (x1 or x2
tank volume gph) using multiple filters will vastly improve the stability
of your handling capability. Another objective is to keep the O2 levels
high in all the levels of the tank.

Along the lines of small bodies being sensitive to small amounts of
nasties in the water, keeping the water clean is probably the highest
priority. Premium filtration alone will not do the job, being unable to
remove many elements which build up. Fry tanks should get more frequent
water changes (% depends on the similarity of source water to tank
water), if the objective is to maximize growth. With fry tanks, I prefer
to used slightly aged water, just to allow it to outgas for a day before
exposing the fry to it. Note that fry are often better adapted to your
particular water conditions than their parents were, but they are less
able to adapt to changes in these water parameters, so stability is key
to their survival.

Fry tank fish-loads of 10"/gallon are easily achievable with the
appropriate tank set-up and maintenance. Mature plant material which
does not displace too much swimming area is also very helpful in
providing a buffering effect, some additional filtering and for
harvesting a significant amount of fry-edible matter (infusoria, plant
matter etc). Following these guidelines will quickly get you into
trouble as all these fast-growing fry will be needing larger homes ;~)

Note that these are working concepts for high-density fry tanks, which
can be applied (as applicable or desirable) to low-density fry tanks, but
they are certainly not pre-requisites to raising fry. In a low-density
fry tank, provide stable water temperature & parameters along with a
steady supply of food, and you will have some success. jmo

NetMax