It can be frustrating when you have invested in an upgrade (it might be better nutrition, a new filter or light, etc.) and instead of better growth and coloration, things don’t seem to improve (or even seemingly worsen).
Of course, not all intended upgrades are beneficial. In fertilisation, less can be more as we describe here. Improved flow is generally good….unless overdone. And better equipment would not help if water parameters do not match the needs of the chosen plants.
But even where the upgrades are sensible, the immediate result can sometimes be confusing- accelerated deterioration on older leaves for instance.
This is because as plants adapt to the new tank conditions, they may hasten the shedding of old leaves.
Plants renew themselves continuously in this way, by producing new growth that is optimised for the current environmental conditions, while letting go of older growth.
In the picture above, the decaying Anubias leaves would not get better, even with, for instance, better nutrition. Instead, the plant is likely to shed them faster, and focus on developing healthy new leaves instead.
Even when the leaves do not deteriorate faster, older growth generally do not simply transform for the better. This is illustrated in the picture above, where the portion of the variegated Rotala macrandra grown in less ideal conditions remains differentiated from the newer portion grown with better nutrition and tank conditions.
For fast growing stem plants, the solution is simple- we replant the healthy top portions after they grow tall, and discard the old stem and roots.
For swords and crypts, older leaves can be trimmed ( especially the ones that are algae-infested) to make room for healthy new shoots.
For very slow growers like Anubias and Bucephalandra, still-healthy leaves often get better but leaves that are too far gone may deteriorate further. This adaptation process takes a long time- several weeks in a tank with CO2, several months in tanks without CO2 injection.
This is an incredibly long period, often beyond what we have patience for!
The leaves of Alternanthera reineckii above are still fundamentally healthy and the algae can be quickly solved over a few days by spot dosing APT Fix.
However they may not regain their sheen and coloration fully. Some scars would remain. In many ways, leaf damage is always permanent, as the plant focuses on new growth, not healing old tissues.
For a deeper dive into managing older and/or damaged leaves, go to this article here.