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[APD] Re: cardinal schooling behavior

> Karen & Reggie, I didn't know that about cardinals, and might get some one
> day if I see some doing that in smaller schools as I have a South American
> themed tank. Those I have seen in shops weren't schooling or I would have
> got some.

You need a big school in a tank that is long enough for them to run in if
you want them to school well.  That is true with most schooling species.  By
a big school, I don't mean 6 or even 12.  I mean 20 or 30 or more.  Most
people don't buy enough to see good schooling behaviors.  A 4' tank will
encourage some schooling, but not a lot.  A 6' or longer tank works best.
Store tanks, especially for little fish, tend to be MUCH smaller than that,
which keeps the fish close enough together that they don't need to work at
get closer.

> Some neons I once had did not school.  I got rummy noses because
> they are also alleged schoolers. But they were not grouping well once they
> got over their new tank. I found by accident that having a moderately
> aggressive fish in there with them makes them school more tightly eg
> fish which is a pushy fish chaser and gets worse if its target is chicken
> like rummys. After removing the aggressor they remained persuaded to
> So I use the pengiuns like sheep dogs to train and condition the rummys. I
> would guess tank fish may become too relaxed in benign company to school,
> rather than genetically degenerate !

These fish are never truly relaxed unless they are in the company of many
others of their own species, no matter how benign the community.  Certainly
they will school tighter if threatened, but remember how HUGE the flooded
forest is.  The volume in even the biggest home aquarium is completely
insignificant.  A wild school of cardinals (or other schooling fish) would
never be confined (or schooling within) such a small area.

> The text book explanation for schooling generally is predator defence in
> that it lowers the chances of an individual fish being eaten because it
> less chance of being targetted, so it makes sense they would school under
> threat.

True, but they don't ONLY school in response to a direct, current threat.
Horses and deer also remain in a herd whether there is a threat present or
not.  If you're not within proximity of your herd or school, you can't get
INTO a safe area quickly enough and you will definitely be lunch.  Likewise,
cardinals do not need a threat to ball up.  They do it even without a
threat. Not all the time, but they still do it.

> Apparently cardinals need to school to develope colour.

Where did you hear that?  Even dead cardinals are bright!

> When coloured up the
> cardinal is not exactly well camouflaged which might play a part in the
> evolution of the behaviour as bright fish may attract predators.

Why do you think they would want to attract predators?  I think it is much
more likely that cardinals and other black water fish are brightly colored
so that they can FIND each other to school in the extremely dark water.
When you see these fish in the wild, even with their bright color, they
don't exactly stand out.

> Why it has
> such bright colours in both sexes in the first place is a puzzle. I dont
> know enough about them to answer that.

There are many species of fish, even brightly colored ones, where the males
and females are similarly colored.  Sexual dimorphism is one reproductive
strategy, but it is certainly not the only one.

> But maybe penguins would work with
> cardinals too.

It is certainly possibly to use an aggressive neighbor to encourage
schooling.  Unfortunately, in the confines of the aquarium, it probably also
causes the fish to live in a chronic state of stress, even if mild and it
may cause the school to spend most of its time out of sight. I have found
that to be a problem when people keep cardinals with discus and large
angels.  The cardinals tend to hide in the bushes rather than face the
larger fish, even if the big guys are well enough fed that they totally
ignore the cardinals.

I recently faced this problem in a 4' Asian tank.  I have had a good sized
school of pentazona barbs in the tank for several years, but recently I
realized that the whole group was always hiding except at feeding time.
When I took a critical look at what was going on, I realized that the yellow
tail rasboras that have shared the tank for the last few years had grown to
over 5" in length.  While these fish are COMPLETELY docile top swimmers, and
never bothered any of the other fish, they are large and swim fast.  Their
simple presence was making the smaller guys nervous.  I removed the big
rasboras from the tank, and within minutes, my pentazonas were out and about
again. (in a school, BTW ;-)

IMO, the best way to encourage relaxed, natural schooling behavior is to
house the fish in a tank that is big enough that the fish want to stay in
close proximity to one another.


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