I'm getting ready to use citric acid to remove what is probably some manganese stains in my pool. In the past I have used an effective stain removal chemical from my pool store guy that he said was sodium erythorbate. However, I've never seen any reference to sodium erythorbate in any stain removal discussions. Does anyone know if this is correct or have any experience with sodium erythorbate as a stain removal chemical. One source indicated that "sodium erythorbate are chemical isomers of ascorbates". Ascorbates are apparently a salt of ascorbic acid. I think this one needs a chemist involvement.