[hahnmeister]

Sunlight will make about 1/4 the heat of a halide/T5 light at the same PAR because with even the most efficient light bulbs, still about 75% of the electricity goes directly to heat. So overheating with sunlight is pretty hard to do... usually. OTOH, if you are in the tropics, you will most likely be providing too much light if anything. Up here in WI, a 14" sola-tube has about the same peak output as a 400 watt halide. Im sure in brighter areas, this peak could be close to a 1000 watt halide. It could simply be too much light.