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Posted by Vreejack on May 21, 2007, 2:19 pm
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> > I have a 29-gal (110-l) heavily planted low-tech tank with 18 fathead
> > minnows (rosy reds, actually), a couple of Ottociclus affinis, and a
> > pair of crayfish. Some of the minnows have taken up the habit of
> > swimming in fast circles along the face of the aquarium glass. Some
> > of the fishes seem to have their favorite spot and one swims circles
> > around one of the suckers that holds my filter intake in place. They
> > usually seem to be synchronized to the music, too, but that is
> > probably a coincidence. Now even the Ottos are starting to do it, but
> > only in pairs. The minnows always swim in counter-clockwise circles
> > as seen from outside the tank but the Ottos do not seem to have a
> > preference. The crayfish just get dizzy watching them.
>
> > Some of the minnows also play a game where they swim towards the
> > filter return outlet from a safe angle until they get caught by the
> > stream and flushed halfway across the tank.
>
> > Watching them swim like this makes me think of hamsters on a wheel.
> > Is any of this behavior cause for concern?
>
> There is an internal fungal disease (Ichthyophonus) that will cause
> disoriented swimming in circles, however this does not seem to be the
> case here. Make sure you have all your electrical properly grounded as
> a phantom current in your aquarium can cause excited behavior in
> fish.
> The usual culprit is a light fixture. A Multi Meter can test for this.
>
> Carl
I've studied a few fish diseases but that's an idea that never
occurred to me. I will have to do some experimenting, then. The fish
appear healthy and energetic and are not bumping into things or trying
to jump out of the water, they just seem to have picked up some weird
habits. It's only four or five of them doing this, by the way. Most
of them are ordinary, boring minnows.
I don't think it's a toxin. They aren't darting about blindly; their
behavior looks almost playful. They aren't staggering or wobbling or
shy, nor have they lost their flight reflex. They aren't hanging
around near the surface nor the bottom unless they think there is food
there. With as much swimming as these fish do on their little
racecourses you would think they would become exhausted, but they
don't.
The only electrical appliances which actually touch the water are the
heater and the filter, but neither of them are causing the behavior.
On the other hand, they only appear to do it when the lights are on,
but the two light fixtures are grounded and are insulated from the
tank. Either one will cause the curious behavior. They act like
solar-powered toys. And yet, if the light were bothering them they
could easily avoid it by hiding under the bogwood or the plants, but
they don't.
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> minnows (rosy reds, actually), a couple of Ottociclus affinis, and a
> pair of crayfish. Some of the minnows have taken up the habit of
> swimming in fast circles along the face of the aquarium glass. Some
> of the fishes seem to have their favorite spot and one swims circles
> around one of the suckers that holds my filter intake in place. They
> usually seem to be synchronized to the music, too, but that is
> probably a coincidence. Now even the Ottos are starting to do it, but
> only in pairs. The minnows always swim in counter-clockwise circles
> as seen from outside the tank but the Ottos do not seem to have a
> preference. The crayfish just get dizzy watching them.
>
> Some of the minnows also play a game where they swim towards the
> filter return outlet from a safe angle until they get caught by the
> stream and flushed halfway across the tank.
>
> Watching them swim like this makes me think of hamsters on a wheel.
> Is any of this behavior cause for concern?