List of Pokemon I Can Catch With the Good Rod in "LeafGreen"by Michael Hines ; Updated September 22, 2017
You can't expect to catch every Pokemon in "Pokemon LeafGreen" without fishing. There are three different types of fishing rods in "Pokeon LeafGreen" -- the Old, Great and Super rods. Each rod catches different types of Pokemon and is an essential item to have if you wish to fill up your Pokedex.
Obtaining the Great Rod
To catch Pokemon with the Great Rod, you must first obtain it. Travel to Fuschia City, located to the south of Celadon City and Lavender town. Once you are in Fuschia City, head south toward the Pokemon Center. To the east of the Pokemon Center you will find two houses. The house on the far right is home to the Fishing Guru, who will give you the Great Rod after you talk to him.
Where to Fish
In "Pokemon LeafGreen" you can fish in any body of water with a shoreline. Many of the game's routes, cities and dungeons have small bodies of water that can be fished. Stop and fish in every body of water you see as each area has different Pokemon with different levels. The Great Rod is designed to catch Pokemon from Level 5 to Level 15.
What You Will Catch
The Pokemon you will catch using the Great Rod in "Pokemon LeafGreen" are Magikarp, Krabby, Horsea, Poliwag and Goldeen. Magikarp are the most prevalent, appearing in nearly all of the game's fishing locations. Horsea is the least likely to be caught, with a 20 percent catch rate in most locations.
Since most of the Pokemon you will be fishing up are lower in level, bring along weaker Pokemon to help you capture them. Higher-level Pokemon will have no danger of fainting in battle, but they will also be more likely to defeat anything you catch with just one hit. Remember when selecting your Pokemon to bring along that all water Pokemon are weak against electric-type Pokemon and strong against ground-type ones.