Fish won't stay in school...

[Jim Hollingsworth]

I have a 150gallon planted tank.
Among other fish I have a school of 12 harliquin rasbora.
My idea was to have them peacefully schooling back and forth in the tank.
They do this once in awhile but mostly swim up and down in the corner of the
tank behind the the filter outputs into the tank. I have tried raising and lowering
the filter output (canister filter). I have also tried using a filter output tube with
more holes to produce much less current. I have also tried using a strip of black
plastic in the corner of the tank to block views or reflections. So far no help.
The fish mostly swim up and down in the corner and occasionally a few of them
go back and forth across the tank. The tank has lots of plants and the water
parameters seem fine. Any ideas?

 

[limwsv]

I have a 150gallon planted tank.
Among other fish I have a school of 12 harliquin rasbora.
My idea was to have them peacefully schooling back and forth in the tank.
They do this once in awhile but mostly swim up and down in the corner of the
tank behind the the filter outputs into the tank. I have tried raising and lowering
the filter output (canister filter). I have also tried using a filter output tube with
more holes to produce much less current. I have also tried using a strip of black
plastic in the corner of the tank to block views or reflections. So far no help.
The fish mostly swim up and down in the corner and occasionally a few of them
go back and forth across the tank. The tank has lots of plants and the water
parameters seem fine. Any ideas?

Tetra schools when they think that they are in danger. If you want them to swim in a school continuously, you will need to supply the danger stimuli.

 

[Tom Barr]

Most tanks that are shorter compress the field of view, so they appear to school better in shallow tanks.
More fish also would help a lot.

 

[JJ..Bequiet]

provide them with a more challenging curriculum, as they may just be bored.

 

[150EH]

I love Rummynosed Tetras for schooling, they never seem to break formation. I currently have a school of 11 and I think I might double that number soon.