If you coat the outside of the tanks with appropriate white or light color….or add a wood or bamboo border around (aesthetics up to you) it will help mitigate soil heat on plant roots. I did tests on them early on but can’t easily find – but enuf to recall it was for the more shallow rooted plants – significant.
BTW, while stuff is ‘rotting’…after a week or two..I use some of the water as a ‘tea’ to ‘dress’ the plants instead of chemical fertilizer. BIG diff. All works out somehow. Unfortunately, still taking care of elderly (90’s) father..so my garden is, of necessity, and again, much smaller this year. Grapevines not clipped back correctly, espaliered apple trees running amok…always something — but nature is so resilient. I love.