The first thing to consider is whether the tank will be on the first or second floor. A larger tank (over 100 gallons) may be unsafe on the second floor if placed in an area where the floor cannot support its full weight. Once a tank that size is filled with salt water, rocks, sand and equipment, it may weigh as much as a small car. If you know the direction of the floor joists, try to place the tank perpendicular to the floor joists. If you have doubts as to whether your upstairs floor can handle the weight, consult a carpenter or structural engineer. Most modern homes are designed to bear that kind of weight, but in situations like this it is better to err on the side of caution.

In some publications, they recommend that the tank be kept out of direct sunlight. The logic behind that is the infrared light from the sun can cause the reef to overheat. For small tanks, this may be an issue, but for larger ones, direct sunlight may be very beneficial to light loving corals. As good as the lighting technology is today, nothing remotely compares to direct sunlight in terms of quality of spectrum and intensity.

If possible, keep the tank at least a foot away from the walls. Some people prefer having the tank flush against the wall, but it becomes a nightmare to service when wires and tubing are crammed behind the tank. It is very helpful for maintenance purposes to have the tank away from the wall so you can get all the way behind it.