Fish only swim on left side of tank. Why?

perhaps they're radical rightists and they're facing the opposite direction? everyone knows those right wing extremists stick together.
 
Is the filter return on the right side?... perhaps they don't like the current making it more difficult to swim?

Is it too hot over there?

Both the heater and filters are on right side of tank. Right side of tank has no duckweed or floating plants due to flow and left side has a ton and it is 100% still water. Agressive bn pleco hides closer towards the middle in the far back behind the driftwood but slightly right-sided.

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Both the heater and filters are on right side of tank. Right side of tank has no duckweed or floating plants due to flow and left side has a ton and it is 100% still water. Agressive bn pleco hides closer towards the middle in the far back behind the driftwood but slightly right-sided.

Shade and calmer water has my vote.

If the left really is 100% still water, beware of dead spots in your tank where mulm will accumulate due to a lack of current.
 
Hilarious answers!

My fish usually stay at the side we feed them. Always left. Radical leftists, as the others say.
 
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