in summer 2 300w heaters moved my 3.000l tank up 2 degrees over an 8 hr period
passing the water through 30m of 25mm black alkathene pipe coiled on the top of tank increased temp by 12c in the same period
good topic
i had an outside rockpool that had partial shade and had no issues with it
maybe different with tropicals as they may have higher light levels in their natural habitat
PIMagnumTetra says that after some private investigating, eyebrow raising and moustache trimming he has found from kidsgrowth.com that this is what really killed the dinosaurs