Unfortunately, I made a big mistake. My iodine level is 700 micrograms, which is very high. Do you know a solution to this? The water is 2100 liters, replacement is very difficult.
You mean 700 ug/L? Normal is about 10x lower, but I don't think it is likely to be a problem. There's no way I know if to remove it, assuming it is iodide or iodate. Growing algae will consume it.