Edward said:
There is no connection between real red plants and Iron fertilization. Red plants are going to be red no matter what. What could look better is bright green and overall structure and health.
Tex Gal said:
I have been adding extra iron for about 2 months now. I have noticed better growth and my reds are very red.
In just cruising Google books for stuff, like
this, if Iron is >75% of chloroplast and folks can measure Iron in dry weight plants in concentrations at around 50ppm (mg/kg), it makes sense that it would make whatever color your plant is a brighter, healthier color of that color... or something. (Shade?) I also believe old circulated signs of Fe deficiency were accurate: yellow veins and pale new growth.
In my experience, when I grew say ET or Glosso they looked a great green with daily Fe dosing. When I grew R. Macrandra it was a great (
hot) red. Green plants will be greener and red plants will be redder. My indicator now is yellowish not limeish growth from HM, for example.
However, when folks attribute miracles or high macro uptake to dosing high amounts of Fe, you should keep in mind what a lot of those folks are actually doing is dosing lots of Fe from comprehensive mixes and using Fe as a proxy for all trace levels. (And I think most of us would agree keeping mobile and immobile traces around is good.) You should not attribute that directly to Fe.
(Tom's great Fe articles and work obviously isolated Fe. I'm typing about annecdotal experience from fellow regular people.)
However, the only thing I've gotten from underdosing (isoltaed) Iron is the pale growth above. The only thing I've gotten from massively overdosing Iron was awesome dark brown colored spots on my hardscape and glass. Good Iron dosing means means good plants, but in the troubles described above I don't think adding a couple tenths of a ppm of Iron will matter or be the cure.
FWIW, of course.