My Vandas got fish water/poop all Winter long.
Regarding their exposure to Sun and heat, we saw blooming Vandas everywhere in Thailand on porches and such, roots waving in the hot Summer breeze. A friend who grew up in Malaysia told me that their driveway in Kuala Lumpur was lined with blooming Vandas. ( that must have been a sight)
He always grew the prettiest Vandas here in NJ outside and he flooded them at least once daily in hot weather and fertilized weekly. I grow mine here in NJ always in the sunniest spots, water daily. I have always grown them also with their roots hanging free, hanging either from a basket or without any anchor.