Can you get a deepseascale in Pokemon FireRed?

You cannot get a Deepseascale in Pokemon FireRed.

Here's why:

* Deepseascale is introduced in Generation IV (Diamond, Pearl, Platinum). FireRed is a Generation III game (Ruby, Sapphire, Emerald).

* The item is associated with specific Pokemon introduced in Generation IV. The Deepseascale is used to evolve Clamperl into Huntail.

Therefore, you wouldn't find this item in FireRed.