Although you haven't specified you query by highlighting an issue, I would advice you to prepare the broth and add 2% of agar powder in it as solidifying agent but while adding the trace metals, you should add EDTA prior to adding Ferric Chloride otherwise the hydroxides formed post autoclaving will leach iron out of the medium. It is also possible to add FeCl3 after sterilization in which case you need to prepare the ferric solution with EDTA in presterilized water. However, in case of Guillard medium the vitamin solution is always added post sterilization .