Hello again. First of all, it is perfectly acceptable to use Metal Out for maintenance, such as when adding tap water, per the labeled directions.

But, I am surprised that you could have added enough iron to the pool by simply adding 1" of tap water to cause staining. Usually, iron accumulates from tap water over a span of time, because there's not that much iron in Baton Rouge's Water.

Could the iron be coming from some other source?