Download What Pokemon Need A Dragon Scale To Evolve Background. Kings' rock can not only evolve poliwhirl into the froglike politoed, it also turns slowpoke into slow king. You probably won't ever have enough sinnoh stones but you'll only need a couple upgrades, even if you keep a living pokédex.
You will still need the appropriate amount of candy if you want to check out the other evolution items in pokemon go and what pokemon they evolve, check out our guide over here.
You find dragon scale in the isle of armor dlc expansion, in the area called honeycalm sea. Here's how you can use the dragon scale special item to evolve seadra into kingdra in pokémon go. A scale that can make certain species of pokémon evolve. I know you need a dragon scale to evolve it but are there some places that are better than others to find a horsea with a dragon scale?