Gee, I thank heavens we don't have woodworm problems in Canada.
If you have an older, well-built house - and anything not well-built won't last in the temperature extremes and potential for ground heaving on the Prairies - you're pretty much good to go.
I had to move back in with my parents after my marriage broke up, brought the queen size water bed, thank gawd, because that helps in my tank arguments.
After being injured at work and then getting a nasty medical diagnosis, I wound up back in with my parents, and have a number of smaller tanks upstairs with no problems, at the moment: a 35 gallon, a 25 gallon, 3 - 15 gallon, a 10 gallon, 3 - 5 gallon, one 3 gallon, a 30 gallon still to be set up, a 10 gallon which will be the official Q tank once I've redone the silicone, and a 3 - gallon downstairs to come up - but, boy, do I need more tanks...
Doesn't seem like very much to me, and they're all relatively small, and all against walls, mostly against outside walls.
But placing a board under larger tanks to spread out the weight would be a very good idea.
Edit - caught one typo, don't know how many got away...