In my experiences, heavy doses of Excel, especially the doses used to spot treat certain types of algae, can have a poor effect on the following plants.
Alternantera reineckii (leaves scar and fall out, stem becomes weak)
Hemianthus micranthemoides (same effect)
Nymphaea lotus zenkeri var. red (leaves scar and fall off)
Some crypts (effect was more mild, algae left scarring on the leaves, but the plant didn't weaken)
It did get rid of the algae, but I would have been smarter to just remove the offending leaves and address the causes. The A. reineckii especially took time to recover and never reached the level that they were at pre-dosing. I do not know why it effected these particular plants in my case.
Now, it might have been me, but I did not notice any changes in other plants, but I haven't kept the entire body of aquarium plants. At any rate, I'm a little leery of dosing excel for spot treating algae, especially when I keep the above plants. I'd rather try and figure out what's causing the algae and remove it that way. It's worked wonders for others, but perhaps my problems stem from my water chemistry or something.
I still don't discourage others from dosing Excel, but I usually do relate my experiences and let them decide for themselves. The possible risks to a few species may not out weigh the prospect of algae removal.
Do you have snails in your tank? Snails are partial to lily leaves. I see a new leave emerging, so that's a good sign. I would worry more if I didn't see a new leaf stalk. Could be that the particular leaf is old or the plant is adjusting, or even beginning its dormant phase.
llj
