Paul - I'm getting pretty obsessed with iron lately, too. I'm seeing less of a number of problems since I increased the dosage, but I'm afraid that in *most* of the re-planted R. indica stems, this particular problem is not going away. Every now and again, a stem will continue to grow from the same tip, but only after putting out a few puny leaves, first. Looks weird. Sometimes, I even take a cutting from this 10-gallon and plant it in my 2.5-gallon tank with 8W NO fluorescent lighting, Flourite, DIY CO2, and basically close to the same dosage of iron as the 10-gallon, just scaled down. I even leave the cutting tall enough so that the tip is close to the light, but the same problem occurs, except that it takes longer for the new branch to make its appearance. Would it help to boost the iron at the roots? Like root tabs that contain iron?
John!!! Hi!!! It's so good to see you here. It's been a while since we've been in touch. Last time, you were still using plain gravel in that 15-gallon(?). Those reds were incredible! I saw you post somewhere that you replaced it with richer substrate. Believe it or not, I'm dosing Flourish Iron in my 10-gallon at 1.25 mL *per day*. On top of this, I'm adding about 10 drops of Flourish; I think this contains iron, as well. So while I think that this is actually enough iron for most of my plants, it still appears to be on the low side for others. This may be why my Alternanthera reineckii has NEVER looked good in my tank. The lower leaves of my M. umbrosum get ratty really fast. And M. matogrossense has been experiencing a slow, excruciating death - I'm down to the last two stems, which I'm sure are going to die very soon.
So are you saying that you only replant the top 2" of the cutting and let it branch out? I guess that's a way to do it... It's really a shame, though, that the beautiful, full-grown stems can't just be replanted and expected to continue its beautiful growth. If I could grow out 5-6 stems at the same time, I could always try to sell them. But it just never seems to work out this way.
Anyway, thanks. I may try dosing an additional 0.25 mL iron per day and see what happens. But I'd be a little worried about adding more than this.