Get the underwater plants established before adding the craws. You need underwater plants like American Pondweed, Sago Pondweed etc. to get established before adding the craws. Or be prepared to annually stock Tilapia OR spray the FA every two weeks.
Does this mean that without other plants growing, FA will take all the nutrients and flourish?
I think esshup's advice is two-fold. Yes photosynthesizing organisms are going to compete for nutrients, so try to get as many nutrients going into plants you like.
The other issue (I think?) is that it is difficult to get bottom-rooted plants established in ponds with heavy crayfish populations.
