Algae all died ...

[DaveC]

So I had 1\2 of a 20L filled with beautiful Red Ogo Gracilaria with 2 grow lights. I still had high Phosphates so I added a GFO reactor. My Phosphates dropped and are currently around .144 and dropping still. Unfortunately most of the algae died.

My target PO4 is .018 and the question I have is, will I be able to grow macro algae with numbers that low?