Hi all,
In my limited experience, red plants get redder the nearer they get to the top of the water and therefore closer to the lights. This suggests light intensity is an important factor especially in deeper tanks.
But once transitioned to submersed form it reverts back to green.
Plants usually produce the red anthocyanin pigments in high light situations, mainly to protect their chlorophyll from damage by excess sunlight. This is from Gould, K. (2004) "Nature's Swiss Army Knife: The Diverse Protective Roles of Anthocyanins in Leaves."
J. Biomed Biotechnol. 2004(5): pp.314–320
By absorbing high-energy quanta, anthocyanic cell vacuoles both protect chloroplasts from the photoinhibitory and photooxidative effects of strong light, and prevent the catabolism of photolabile defence compounds. Anthocyanins also mitigate photooxidative injury in leaves by efficiently scavenging free radicals and reactive oxygen species.
I think
@Oldguy &
@zozo are right, because water is pretty effective at attenuating light, as you move away from the light source plants have less reason to become red.
High light and high conc of traces seemed to work for me.
I don't know enough about the biosynthesis of anthocyanins to pass comment on which micro-elements may be effective, but it might be an iron (Fe) or copper (Cu) effect. Anthocyanins don't contain any iron (Fe) but there is plenty of anecdotal evidence that high iron levels enhance red colouration in leaves, <"
possibly by reducing PO4--- availability">.
If I was aiming to keep red plants red, I might try just lower nitrogen levels, purely because the anthocyanins are retained in the cell vacuole and if you have a lot of chlorophyll in the mesophyll layer it will mask the red pigments and the over-all appearance will be a dark green colour. The chlorophyll molecule contains four nitrogen atoms and <"
leaf colour is a pretty good indicator of nitrogen content">.
This works with Amazon Frogbit (
Limnobium laevigatum), where high light, slightly nutrient deprived, plants develop red "tiger stripes".
You would have to balance plant growth and nutrient level (probably aim for "3" on the LCC chart above).
cheers Darrel