bizarre jumping behavior!

[Jason]

I've noticed that one of my gold barbs keeps on swimming furiously
towards my filter outlet (where the stream is at its fastest) and then
jumping up, smacking his face against the plastic screen of my lamp. It
seems like he's having fun, but is this normal? He's literally
developed a reddish bruise on his face (above his mouth) but he keeps
on doing it.

I have a 12g Nanocube, all levels normal (no ammonia, nitrite, 20ppm
nitrate, stable pH of 7). Frequent water changes.

The only thing that's changed is that I added 2 new plants yesterday.

The fish haven't been hungry, and have virtually ignored the food I
give them (they're usually hungry all the time) but I've been feeding
them a lot the last couple of days because I'll be away for vacation.
Is there anything I should be worried about?

[Flash Wilson]

On 23 Dec 2004 13:49:02 -0800, Jason > wrote:
>I've noticed that one of my gold barbs keeps on swimming furiously
>towards my filter outlet (where the stream is at its fastest) and then
>jumping up, smacking his face against the plastic screen of my lamp. It
>seems like he's having fun, but is this normal? He's literally
>developed a reddish bruise on his face (above his mouth) but he keeps
>on doing it.

Is it near a glass side? My fish sometimes go nuts about their
reflection or chase the reflection of bubbles up and down the glass
etc... Could you screen the surrounding area (internally by plants,
externally by putting dark coloured card on the outside of the glass)
so he can see what he's hitting a bit more clearly? Perhaps he sees
some movement somehow and mistakes it for feeding time?

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[Jason]

S/he and the other fish sometimes "play" against the glass, probably
seeing their reflection, and dance up and down the glass, especially
near the bubbler, but this was different. He was aiming towards the
filter output jet (no reflection from the glass) and then he would
shoot up, hitting the light shield.

Eventually he cleared the barrier to the back compartments of the
Nanocube, and I spent about 20 minutes trying to coax him out and back
into the main tank.

He had a huge red bruise on the front of his face, but I came back from
a holiday trip yesterday, and he seems to have healed.

May not ever know what possessed him to do that...other than the
thrill. :-)