inline pump keeps water cooooool as can be. No residual heat sitting in the res. There's no chiller on this one, but it sits on concrete. Also, flooming.
I really like your system and your roots look very healthy.
About the inline pump, I wonder if it makes a huge difference if the pump is in or just above the water.
The water that flows through the pump is also meant to cool the engine.
So water that comes in at one side will leave the pump a tiny bit warmer at the other side.
The heat that leaves the pump via the air, will heat up the air a tiny bit. This air will also heat up your water and system as well.
It are all little bits of course.
The law of Conservation of Energy says that energy (heat) remains constant in an isolated system.
Let's say your growroom is an isolated systems.
Of course there might be a chance that the warm air looses some of it's heat when it touches the walls.
Did you ever measure for a longer time if the water stays cooler when you have your pump above?
And also what the difference in temperature are in the air.
I am really curious, because I like your set-up and thoughts about it.