Rust stains in the plaster are unsightly! One way to get rid of the stain is to drain the pool, chip out the stain down to the re-bar, cut out the iron that is causing the stain, and re-plaster the void. This process is time consuming and costly. The alternate method is to buy a ceramic fish to cover the stain, glue it over the area with under water epoxy. This requires a pleasant swim to adhere the tile. The time is cut drastically, and the expense is minimal. The stain is now covered with nice looking detail that will last for years. Enjoy the pool!