As long as the weight is distributed well over a good stand (not the wrought iron type that just have 4 legs) a 45 gallon should be fine in most houses. I don't know what the dimensions are for a 45 but a standard 55 is about 4' x 1'. That's about 600 square inches of base. The water weight of a 55 gallon is about 470 lb plus tank and stand brings it to about 600 lb. That's only 1 lb per square inch on the floor. Not much to worry about.