Cloyster (Japanese: パルシェン Parshen) is a dual-type Water/Ice Pokémon introduced in Generation I. It evolves from Shellder when exposed to a Water Stone.

When should you evolve Cloyster?

No need to wait to evolve it since Cloyster doesn't learn any strong moves past level one. All you have to do is bring it to the Move Reminder at any Pokémon Center, so don't waste your watts on Hydro Pump at the Trader. The ideal move-set for this Pokémon would be Iron Defense, Ice Beam, Hydro Pump and Blizzard.

Is Cloyster a good Pokemon?

Cloyster is my absolute favourite gen 1 pokemon. His lack of hp leaves him overshadowed by lapras and dewgong, but he definitely gets the job done if you're good at dodging. Use him to slay dragonites and acid-using grass type pokemon. He only works with good dodging though, I can't emphasize that enough.