Rust is actually the oxidation of iron.
As the rust corrodes is iron being released into the water?
If this is the case, perhaps dosing Flourish Iron is not needed.
It's worth a thought isn't it?
Is the this process harmful to fish?
I don't know.
But here's an interesting find:
.....Many fisherman believe that
.....it is important for a hook to
.....rust so that it falls out of the
.....fish’s mouth before it harms
.....the fish; however, studies
.....actually appear to indicate
.....that it is the toxins in the
.....rust and corrosion itself that
.....is harmful to fish.
.....Emperor, http://www.sport-fish-info.com/html/emperor.html