very welcome my friend.
And indeed... this is not to say that home-grown phyto is bad. Its not a matter of good versus bad. But rather (IMO) good versus better. What is "better", though, is to be determined by the end user. For me... it is time savings and edge on quality that draws me to commercially produced phyto. If I needed (very) large quantities, or simply liked the challenge of tinkering, I may well indeed culture my own.
As for rotifers... yes, please! Do always culture zooplankton when possible. Copepods too (see the Marini article in Adbanced Aquarist e-zine, and the Rhodes article on copepods in the Conscientious Aquarist e-zine).
A majority of the corals we keep are carnivores and will benefit by such plankton.
FWIW... I culture my live copepods on bottled phyto
I will keep digging for the info on temp influence on nutritional value of cultured phyto.