Here is a look inside the RAIN4 dome lid, with all 6 of the GEM5® lights plugged in. The photo had to be dimmed (edited) because the lights are blinding bright 660nm deep reds, and put out 5 watts each (30 watts total), which is almost all illumination because the power supply boxes are safely a far distance away (see
www.LEDsafety.org) and do not add any extra heat at all to the scrubber.
Other people's lights, such as the common bolt-on ones from China, have the power supply inside the light, and this makes the lights 60 or 80 watts of heat each, but this is just power supply heat and not illumination, and so the scrubber gets very hot (120 to 300 watts of heat) which makes your sump area a warm swamp.
When a RAIN2 or RAIN4 is new, you only plug in 1 light because they are so bright...