atomweaver wrote:
Zëbulon wrote in
:


"nut" wrote in message
. ..

Zëbulon wrote:

"Tynk" wrote in message
legroups.com...

You cannot set such a vague "rule" when there are way too many
variables when it comes to stocking a fish...much more than it's
size in inches.

======================
Such as the fact a 1" goldfish passes a lot more waste than a 1"
guppy.

The rule was for tropical fish, not coldwater.

=================
This is true but how many newbies know that? They come here all the
time asking about putting tropicals with goldfish. Some people keep
them together successfully.

Also, some tropicals have a lot more bulk per inch than others.


It would be good to have something a little more accurate than the inch
per gallon guide. In one article I read, they made the excellent
suggestion that the "real" main limiting factors for an aquarium are
mass of fish as adults vs. water surface area of the tank (which is a
more measurable equivalent to oxygen transfer rate), with different
stocking ratios for Fresh, brackish, salt, (and warm and cold) waters.

You could further modify this by multiplier factors considering things
like whether additional oxygenation/waste management is available
(airstone, planted tank etc), or fractional multipliers for if you're
keeping only carnivorous fish (more waste). The main advantage is that
you get a better feel for the differences in body types. The drawback
is that I haven't found many sources which report average/typical adult
fish mass. This is one of them;

http://www.aquariumfish.com/aquarium...aid=323&cid=53
&search

For common freshwater species, that table gives you neons at 0.2g and
7cm discus at 19 g. If anyone knows of other resources which report
more adult typical mass values for FW aquarium species, I'd love to see
it. I could bring my fish into work, and weigh each immersed in a fixed
volume in a graduated cylinder (and then weigh the water afterwards to
calculate their mass), but I'd rather save them the stress of such a
trip.

Even after all that, metabolic rate doesn't scale directly with mass of
the fish, but this would be a step in a more accurate direction.

DaveZ
Atom Weaver

As you said, "water surface area of the tank (which is a
more measurable equivalent to oxygen transfer rate)". Oxygen is one
limiting factor, but this should be determined by the
filtration/oxygenation equipment you have in the tank, not surface area.

Another fish-keeping myth is that "fish grow to the size of the tank".
There is some truth in this, although I haven't figured out the
mechanism yet. Perhaps the water quality determins the size of the fish
and as the fish grow too large for the tank/filtration system.
Consequently there is a higher level of nitrite or some other factor
that slows the growth of the fish.

In any case, if you put in a filtration/oxygenation system four times
the recomended size, you can support more fish and your fish will grow
faster.

In other words, your recomendations for rules of fish stocking needs to
take into account factors such as water flow rates, filtration
effectiveness and oxygenation.

On the topic of measuring fish, I always have trouble with the method
you mentioned. I find it is easier and more accurate to measure the
length of the fish and the estimate its mass by interpolation. But
then, I'm a bit of a klutz and my students are even worse. (I first
discovered the effect of incorrect filter sizes on growth rates when I
disassembled the tanks we had used for a growth rate experiment that
failed only to find that the students had mixed up the filters and that
the filter sizes explained the strange results).