When will FIX / FIXLITE not work?Updated a month ago

When plants suffer from overcrowding, they weaken and FIX / FIXLITE will not help. An example of overcrowding is shown here: 

If your tank looks like the picture below, APT FIX / APT FIXLITE will not make any visible / meaningful difference. You can use a copper-based algicide, which will indeed kill all the algae. However it will also destroy the tank's bacterial colony and other plants. For such a tank, we recommend a reset.

Old leaves that are deteriorating are big algae magnets. Plants abandon old leaves and focus on defending new growth. Old leaves have limited capacity to recover once they start to deteriorate, and it is better to cut off these old leaves and allow the plant to channel energy to new growth. It is not worth treating all the deteriorating growth with algicide as deteriorating leaves will not recover in the long run even if the surface algae was removed.