Is there a chemical way to remove a calcium ring on a pebble tec salt water pool?

Yes, there is a chemical. As long as you clean the tile while the calcium is just a film. Use "Biodex 300" follow the instructions carefully to avoid injury.Once the calcium or hard water deposit has become thick it must be removed profesionally. There are many debates about what method should be used, as some may cause dammage to the tile. The use of Biodex 300 can stain the substrate. I have been a professional pool tile cleaner for many years. The absolute safest way to remove the calcium is to dry soda blast it.