With so many Pokémon to keep an eye out for in Pokémon Brilliant Diamond and Brilliant Pearl, it can be difficult to remember all the small differences between them. You may encounter Shellos of different colors and his evolved form, Gastrodon, as you battle other trainers and explore the Grand Underground. What are the shape differences between Shellos and Gastrodon in Pokémon Brilliant Diamond and Brilliant Pearl?
We can confirm that there are no differences between the two different forms of Shellos and Gastrodon. These Pokémon simply have two different colors that you can find while exploring the Grand Underground. Both of these Pokémon are Water-type and Ground-type, and if you fight them, you'll mostly want to use Grass-type attacks to hit them with the strongest attacks possible.
You just have to catch one of these Pokémon to make it count in your PokéDex. It is not necessary to capture both versions to count because they are considered to be the same Pokémon. Given the color and physical differences between them, it might blow your mind, but don't worry, they are considered the same in your PokéDex. Both can be found in the Grand Underground as you explore this region. A Shellos will evolve into Gastrodon of the same color.