All trees are outdoor trees and therefore require a large amount of light. We call tropical trees indoor trees only because they cannot survive in temperatures below 50 degrees. You should place your tropical tree outside during the summer to get revitalized. This will help it stay healthy and prepare it for its winter stay indoors.
There are several factors to consider when placing your tree indoors. Never place your tree over or directly under a heat source. Since these are tropical trees they need some humidity, and placing them close to heat source would be like planting them in the desert. There are several ways to increase the humidity around your tree. You can place your tree on a humidity tray, and, or mist your tree at least once a week. When placing on a humidity tray add some gravel to keep the base of your pot out of the water.
The holes in the bottom of your pot not only allow the excess water to drain, but they also allow oxygen to the tree roots. Do not place your tree behind a closed curtain at night. The drop in temperature between the window and the curtain will severely stress your tree.
Indoor light levels are much lower than outdoors, even in a south facing window. The glass from your window filters out many of the UV rays that a tree requires for photosynthesis. The results of this are larger leaves and long leggy growth. This is why your tree needs to spend its summers outdoors. Depending on the variety of your tree you may need an additional light source. A regular fluorescent light, or grow light may be required. They should be placed approximately 6 inches from the top of your tree. Light levels drop very rapidly from there source, the further away from the light or window, the less effective they become. In most cases some sort of artificial light will be needed for at least 8 to 10 hours a day.
Indoor or outdoor at some point your tree will be in the open air, free from the confines of winters grasp. It is at this point that you need to decide where to place your tree. All species require different levels of sun exposure. As a general rule, full sun to a bonsai does not mean 14 hours of blazing hot August sunlight. Unless of course your bonsai is a cactus. Morning sun with protection from the hot afternoon sun works in most cases. Keep in mind more sun equals more water. I recommend turning your tree from time to time. This will help to keep the branches from reaching toward the sun and creating bare spots on the back.
One other thing to consider when outside is the environment. Do your neighbor kids play kick ball against the side of your house? Will the deer, squirrels and chipmunks have a feast? I know for a fact that the birds like to remove the moss looking for bugs.
“Behind the cloud the sun is still shining.” Abraham Lincoln