[dinthbrgh]

Hi all,
Just a couple random questions because I'm curious about my fish. Maybe you folk will know.
1. Why do Tetras swim with their bodies tilted slightly horizontally? At first I thought my Congo's were sick, but they've been swimming that way for years, and now I have noticed that the new Lemon Tetras swim the same way. My Rainbows swim perfectly vertically always.
2. Why don't my schools school? 5 Congos and 10 Lemons and they're all over the tank. Even when I had 8 Praecox, they swam separately most of the time. And when they did occasionally school, ALL of the fish schooled together; the entire tank! Rainbows, Tetras, everybody.
3. Why do fish occasionally swim up and down the glass...especially up and down the corners?
That's all.
Thanks.

[Colin_T]

Tetras should be horizontal when they swim. If they are swimming with their head up or down a bit they might have just eaten and have a bit too much air in their body to maintain a nice balance. Thus causing the odd swimming style.

In the wild tetras occur in groups of thousands, sometimes even tens of thousands. When you isolate one of those fish the individual will panic and swim about on their own until they get eaten. Hence the reason they stay in large groups, safety in numbers.
In an aquarium there is often not enough fish of the same species to be able to make a normal school. And there are no predators to eat the ones hanging around by themselves. Having larger groups of tetras, (ie: 30 or 40 lemon tetras) will encourage them to school. They become like sheep and where one goes, the others must follow because they don’t want to be left alone.
Also if the aquarium isn’t that big many schooling fishes won’t school either because they feel comfortable in the cosy little tank. The opposite can be true if you stick a small number of individuals of one species into a really large tank. The fish often go and hide in a corner and never swim out in the open. If there were more fish for the school then they will encourage each other to come out and move around the tank.

Fish don’t know what glass is and neither do many other animals and even some people, (like me when I walked into a glass door that had just been cleaned). It is an invisible barrier that stops them going where they want to. An aquarium is a small place for fishes to live. Fish like tetras have huge rivers to swim about in and might travel miles upstream before coming back the other way. They try this in an aquarium and can’t work out what is stopping them from going where they want to go. Ergo they swim up and down the glass in the corner.

[JG]

I don't know if this is what dinthbrgh means, but I have some Sundadanio axelrodi and they swim a little canted. One eye is up, one eye down... I always figured they were simply watching for predators at the surface and food at the bottom. They are pretty small fish and presumably have to be careful not to win a "Darwin Award".

Of course I could be wrong about why they do that.

[dinthbrgh]

Thanks both!
Colin, i get the impression they feel safe enough so no longer need to school. They did the first couple of days. Almost seems sad that we put them in little glass boxes. Those congos really pick up speed when they chase each other around! Can't imagine them being in less than a 75g, and even that seems small for them.
JG,
That's exactly what I meant. One eye up and one eye down.

[Justbows]

These are some really excellent, yet rarely discussed questions. I don't think I have ever really seen good answers to either of these questions and have wondered both myself. My educated guesses as to why both these phenomenon occurred were pretty close...but still...nicely layed out Colin. Appreciate it!
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Sincerely,

~JUSTBOWS~

[rainbowbratt]

I know I'm a bit late on this discussion, but I can say I've also seen many different tetras, rasboras, and even bows swim at a bit of a cant.... not completely sideways, and not completely up and down either....maybe a 10-15% lilt? with one eye facing a bit up and one facing a bit down....all the fish in the school swim at the same angle. I've thought it had something to do with the lighting within the tank versus the light outside the tank? or a combo of lighting within and without the tank, and decorations they are swimming around, etc?......I cant really remember what I attributed it to, and now its been such a common occurrence, I dont remember what I decided was happening. lol.

While I'm giving my 2 cents.......I wanted to just drive home the "schooling" fish topic.......schooling fish are used to being in Very large schools numbering in the hundreds or even thousands in some habitats. So, when we are told that keeping 3 or even 6 of each type of schooling fish in our tanks is ideal.....well, I'm sure you guys can plainly see that those numbers are just TOO LOW.

As for schooling fish not staying in tight schools in our tanks.......some of the reasons are already clearly listed above....so, I really dont have anything to add as to why....but I have noticed that the more different types of schooling tetras I have in one tank(I once set up a 125g with All tetras.......think I had about 75 fish in there at one point! I think about 10 different species, mostly the tinier ones like ember tetras, green fire tetras, "black" neon tetras, "green" neon tetras, and some diamonds and "rainbow" emperor tetras too.....anyway, with that mix, it was like confetti all over that huge tank. The fish wouldnt school together no matter what was going on in the tank. I added the schools of fish slowly over the course of weeks.....I placed the smaller fish 1st....the 1st school I put in were the ember tetras. They schooled nicely. I added the green fire tetras.....each type of tetra stayed in their own school, and schooled nicely.......BUT!! As I added more different types of tetras, and they became comfy in their surroundings,..they started just hanging out wherever they felt like it. Stopped schooling alltogether, unless something startled the tank--they they'd ALL school together. Needless to say, the tank did NOT have the look I thought it would and I eventually split the tetras out to different, smaller tanks, according to size and temperament.

Anyway, just some anectdotal info from my experiences...

[dinthbrgh]

Dang fish! Why can't they just stay in perfect little groups so we could arrange our colors just right!

When I had Praecox in the 75 with the Boes bows and the Congo Tetras, they would all school together occasionally, too. Sometimes even the Rams would join in!

[Lisachromis]

I can't recall the exact definitions at the moment, but your schooling fish are not schooling fish. They are shoaling fish. I don't think there are any true freshwater schooling fish.
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Basic Info page

[dinthbrgh]

I thought the only difference between schooling and shoaling was which side of the ocean you lived on. Basically the meaning was the same, but different cultures use different terms.

Anyway...it was interesting to watch when all these different types of fish grouped up and followed the leader, whatever he was. It seemed they didn't much care which fish led.

[Lisachromis]

From: http://en.wikipedia.org/wiki/Shoaling_fish

[Colin_T]

so the same fish could be considered shoaling and schooling.
ie: they hang out together before swimming off in the same direction
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Kicked a black cat? Sounds more like ran over one, backed over it, hunted down its mother and did the same

[mikev]

we need a Glossary. To include terms like these, as well as some abbreviations not everyone is familiar with.

[Colin_T]

what section should the glossary go in?

I started one in the news section
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Kicked a black cat? Sounds more like ran over one, backed over it, hunted down its mother and did the same

[mikev]

That is the easy question...we can always move it from one place to another... the more difficult is to write it (in fact to set it up so it gets written collectively). And I think if it is to include a definition of schooling vs shoaling it should be a real definition, not a quote like now!

[Colin_T]

That sounds like too much hard work
Should I go and photocopy some pages out of my big fish books and use them as the basis

We could probably just let people add stuff in new posts under the same thread. And then one of the mods can move them all together
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Kicked a black cat? Sounds more like ran over one, backed over it, hunted down its mother and did the same