Plankton, invisible to the naked eye, is its main food source. It comes onto the land periodically, but the reason for this is not known. When its natural enemy attacks, it oozes purple fluid and escapes. It apparently had a huge shell for protection in ancient times. It lives in shallow tidal pools.
Pokédex entry #423
Gastrodon in Pokémon GO
It's possible to hatch Gastrodon from an egg?
No, Gastrodon can't be hatched.
Which are Gastrodon’s strengths and weaknesses?
Gastrodon is a ground and water type Pokémon. ground type pokémons are strong against fire, electric, poison, rock, steel pokémons but weak against grass, bug pokémons. They are not affected by flying type pokémons. water type pokémons are strong against fire, ground, rock pokémons but weak against water, grass, dragon, electric pokémons.