GSMGuy:
He is not entirely "false" in stating that the led does not transfer heat into the tank Halides, pc's, and t5's use a radiation based reaction of a gas being in contact with an arc of electricity to produce light, this contact between gas and electricity produces a great amount of heat which will naturally heat up anything in the surrounding area, including an aquarium. LED lights are exactly what the name states via acronym, they are a Light Emitting Diode. LED lights do not contain a filament or electrical arcs, instead they contain a high quality semiconductor material and produce light via the high speed movement of electrons over that semiconductor material. This produces a mere fraction of the heat as ANY halide, PC or T5 bulbs. Now with aquarium grade manufactured LED fixtures such as the AI Sol, there are integrated heatsinks that pretty much dissapate any heat produced by the diode. The only way that a reasonably measurable amount of heat would be dissipated into the aquarium would be from a failing or low quality heatsink (Such as some DIY fixtures), or having the fixture literally a few inches from the surface of the water. additional heat would be added via any t5 or other lighting as many LED users in our hobby use them as supplements to t5 or halide/pc lighting.