My in ground pool on Hatteras Island was covered with five feet of salt water during hurricane Irene. I just finally got down to inspect the house and pool and have found what looks like barnacles growing on sides and bottom of the pool. It's been a month since the pool had been running. Is there a special chemical I should add to the pool to kill these things. I'm closing the pool and would like to kill them so I don't have a problem in the spring