The story introduces us to two Magikarp living in a toxic lake. Correction: the LAST TWO Magikarp of the toxic lake. They want to find a trainer so they can live.(In a ball that is probably only three inches big at best)
Ron finds the polluted pond. However, one of the Magikarp dies.(SPOILER) And then the last Magikarp left gets sick. Luckily Ron shows up just in time to battle the infected Magikarp and win!
You described it well enough for a Magikarp. But every story can use more description... :D
Because this is a Magikarp story, I HAVE to nitpick. You spelled dying "dieing". Also, any number bigger than ten, you use digits. So seventeen should be 17 and thirteen should be... 13. Nearby is one word. But that's nitpicking, so you can ignore it if you want.(Though if you see this, then it is too late)
Magikarp take 2,500 to 5,000 characters. You have 6,160. Honestly, I should've just skipped the rest of the sections and gave you the fish, but that's no fun. :P
It was a tough choice. The entire story was flawed. Magikarp is a god for pete's sake.
Have fun splashing.