It is not possible to get the Red Gyarados in Pokémon Yellow version. You can only get it in Gold, Silver and Crystal version.
Gyarados learns Hyper Beam at level 50.
Magikarp will evolve into Gyarados.
If you are playing the original Gold game: You caught either a Missingno. (I'm pretty sure you didn't) or you caught the Red Gyarados. It's sad, but the Red Gyarados in Gold has a horrible glitch in it that has a chance of doing what you just described. If you are playing Heart Gold: I have no idea what happened. The Gyarados glitch does not occur in Heart Gold.
A golden Margikarp is a shiny margikarp, and as with other shiny Pokemon, there is only a 1/1892 chance of getting a Shiny(golden) magikarp. Breeding a Shiny Gyarados or a Shiny margikarp with another shiny Pokemon THAT CAN BREED WITH GYARADOS/MARGIKARP may have a higher chance of breeding a shiny magikarp. You can also trade the shiny gyarados from Pokemon Gold, Silver, and Crystal version.
It is not possible to get the Red Gyarados in Pokémon Yellow version. You can only get it in Gold, Silver and Crystal version.
There's no such thing as a gold gyarados. its only got 2 colors, Red and Blue
Gyarados learns Hyper Beam at level 50.
Magikarp will evolve into Gyarados.
If you are playing the original Gold game: You caught either a Missingno. (I'm pretty sure you didn't) or you caught the Red Gyarados. It's sad, but the Red Gyarados in Gold has a horrible glitch in it that has a chance of doing what you just described. If you are playing Heart Gold: I have no idea what happened. The Gyarados glitch does not occur in Heart Gold.
A golden Margikarp is a shiny margikarp, and as with other shiny Pokemon, there is only a 1/1892 chance of getting a Shiny(golden) magikarp. Breeding a Shiny Gyarados or a Shiny margikarp with another shiny Pokemon THAT CAN BREED WITH GYARADOS/MARGIKARP may have a higher chance of breeding a shiny magikarp. You can also trade the shiny gyarados from Pokemon Gold, Silver, and Crystal version.
In Pokemon Crystal version, you catch it at the Lake of Rage.
its not in the game only in gold silver crystal
only 2 red gyarados and palkia
you don't get one.but you can in Pokemon gold,silver,heart gold,and soul silver.
If you are talking about the Silver and Gold versions then you can just keep it and battle with it.
There is not a red Gyarados in Lake Verity. The in-game report of a sighting is simply a story mechanic to get the player there. This little story element is a reference to the Red Gyarados in the Lake of Rage on Pokemon Gold and Silver.