Granted, I'm in an older, sturdily built house, but right now I have a 35 g., a 25g, 3 15g., (one serving as a Q tank at the moment, although it's soon to be properly set up) 2 10g., 2 5 gal. and one 3 g. set up in my bedroom, also a large storage container with about 10 gallons of water in it.
I'm in the (slow and long delayed) process of doing a tank shuffle around the room so that one 10g. will be shut down for use as a Q tank, the storage tank emptied and a 30g. set up - then I'd like to convert my closet to a fish room, although there I want boards spread under, as closets aren't built to be weight-bearing to the requirements for regular floors.
I don't expect a 30 g should be a concern - if it is, the house is a hazard to anyone within.
