to the pysducks ;)
Go to Cianwood City, southwest of Olivine City. Go to the pharmacy there, and you'll get a free SecretPotion. Also, challenge the Gym while you're there. Go back to the Ampharos and the SecretPotion will cure it.
First you need the badges from Oreburgh, Eterna, Pastoria and Veilstone citys. when you have all those go to Lake Valor. Cynthia should be standing there. Talk to her and she will give you the item SecretPotion and the Old Charm to give to her grandmother. go to where the psyduck are blocking the way north from Solaceon Town. use the SecretPotion and the psyduck will go away. follow the path until you come to Celestic Town. speak to the village elder and give her the Old Charm Cynthia gave you. then return to Hearthome and Fantina should be there.
You don't give it a stone...
Give it berries, LOTS of berries. and after about 10 or so it should be back to full health!
give it to Kurt he will make a pokeball out of it
A house in Cianwood has a guy who give you a Secretpotion. Use it on ampharos.
The serum you are talking about is actually called a secretpotion. You have to go to Cianwood City's pharmacy. Once you talk to the clerk, he'll give you the secretpotion to give to the Ampharos in the lighthouse.
You can only get the SecretPotion after you have talked to Jasmine in the Olivine Lighthouse. Then she will ask you to get Ampharos some Medicine. You go to Cianwood City and talk to the guy at the Pharmacy and he will give you SecretPotion for Ampharos.
you have to go to cianwood city and go to the top of the lighthouse and find jasmine she will give you the secretpotion.
You just have to climb the light house, talk to her then go to the pharmacy in cianwood and he will give you the secretpotion.
you need to go to cianwood city's pharmacy shop talk to the guy and he will give u the secretpotion
you go to lake valor, where you'll meet the Pokemon master Cynthia. she'll give you the secretpotion, which you spray on the psyducks to get past them.
Your mom should give it to you at the beginning of the game.
After you have defeated leader wake in pastoria city, Cynthia will give you a secretpotion, go to the psyducks and they will go away
You get it from the genie that you meet in Jubilife City if you do not see the genie then you must return the game and ask for a full refund immediately, but before you can see the genie you need to release your starter Pokemon.
Just use them alot in battle and give them good berries and that should make them happy
You go to Cianwood city south of Olivine City and talk to the guy in the pharmacy. He will give you the secretpotion which you then give to Jasmine (the girl with the sick pokemon) and she gives it to the pokemon. After that you can battle Jasmine as she is the sixth gym leader and she uses steel types.