Fishes - as if turned to stone?!?!

Fishes - as if turned to stone?!?!

Rohu fishes in aquarium at St Peter’s College, Kolenchery

These are some rohu fishes in our aquarium. Ever since they were placed into the aquarium they have been acting strangely.

Statue fishes?

The fishes are all standing still, almost vertically, and breathing heavily.

Strange behaviour of Rohu fishes in aquarium

Sometimes they show very slight movement by moving to a new corner of the tank.These fishes are fed properly and the oxygen in the tank is also supplied in plenty. What is the reason for their strange behaviour?