There’s a Facebook group called CO2 Supplemented Tanks I would join, even if not using CO2. Tom Barr is a group member for example. There’s another forum I could PM to you, some top Dutch and Garden Style people are there as well as Yugang, who developed a horizontal reactor that I use. My favorite aquarist, Dutch competition and Garden style winners are there (I keep a journal there as well).
I really like both because people will do writes ups about their tanks, listing parameters and more importantly, their maintenance practices and such.