Any ideas why fish are doing this

[Country joe]

For about 4 months now my fish have been doing this, the Celestial pearl danios all stay under a corner plant only coming out at feeding, and my Sparkling Gourami lives permanently near the top of the water next to the outake tube in a vertical position, and never moves, I never see him any where else in the tank, even at feeding time, and yes he is still alive, there is no bullying as these are the only fish in the tank, all water tests come up fine, they have been in the tank for 9 months, is this usual behaviour, thete are live plants and wood in the tank and ceramic tubes so plenty of hide outs, but are not used.

 

[GaryE]

It's fear behaviour. You'll have to figure out of what.

Is there a backing on the tank? What else is in the room? Are there shaded areas? Is the heater or are other devices leaking current? Is the water clean (that will cause fear type responses).

If there's no backing the fish can feel exposed to imaginary predators. If there aren't regular water changes, fear hormones can build up.

 

[Colin_T]

We need a picture showing the entire aquarium with the light on.
We need a 1-2 minute video showing the fish. Upload video to YouTube, then copy & paste the link here. If you use a mobile phone to film the fish, hold it landscape mode.

What is the ammonia, nitrite, nitrate and pH in numbers?

How often do you do water changes and how much do you change?
What sort of filter is in the tank?
How often and how do you clean the filter?

Is there a lot of water movement in the tank?

Is the aquarium in a loungeroom where people regularly go past or a quiet bedroom?