The heater should not kill anything if set to the right temp and not blowing hot air directly on the plants... The best kind of heater is the ambient kind, (oil filled usually, as I mentioned earlier) this allows warming of the area simply by using the flow of your circulation fan, and distributes heat a bit more evenly. Treat the heater like a light when determining how far away to put it from growth, use the back of your hand to see if the plants are heating up.... :firedevil: