"fish grow" is correct and usable in written English.
You can use it when discussing the growth capacity of fish. For example: "Adult fish can grow up to three times their original size."
"Fish grow their own food, so the system is self-supporting.
There, they could fish, grow vegetables, swim in their own pool.
The fish grow to a maximum length of about 30 centimetres (one foot).
After the eggs hatch in January and February, the fish grow until there is no oxygen left in the lagoon.
That brought the nets right up to the coast, into the shallow water where the young fish grow up.
The fish grow to a large size, attaining a maximum length of about 1.8 m (6 feet).
"Have the fish grown too cold?
All that kicking strengthened Phelps's legs, which was like a fish growing more gills.
The fish, grown in dozens of square and round cages, can be detected only by bubbles on the sea surface.
Marlins are among the world's most prized blue-water game fish, growing to hundreds of pounds.
The foily taste of the fish grows as he swallows the water, brings a sting to his mouth.
