Also I read today that I can fight red algae with Copper.
Don't do it. Those algaecides do contain copper, but they will kill your
plants as surely as they kill your algae. They may also kill inverts like
shrimp or snails, if you have them.
the way should I add Seachem Flourish now? I think I should wait until my
Waiting awhile probably won't hurt. Though personally, the only time I ever
have algae problems is when I run out of fertilizer.
Do you have enough plants? I have some clippings I could give you if you need