Until it looks like a section in a fish store? Its actually a hard question, so to speak.I guess a "fish room" would just be a room with multiple tanks for starters.Depending on the sizes etc it makes a difference also but even if you had 10-10 gallon tanks it would probably look like a fish room if it was a rack system.I have 5 tanks in my bedroom 40 planted,70 tall,30 long and 2 10's~ but that isn't the actual"fish room" but could be considered one...or just be considered the bedroom of a fish junky
I have a 215,a 125 and another 10 in my living room,a 47 bow in my daughters room and then a whole bunch in the actual fish room.100,90,40 breeder,33 long,32 breeder,30,29X3,20 longX6,a 55 and 3 10's and I think I forgot a few...approx. 1,500 gal pond ... if I had a basement you would not be able to see walls.I guarantee that.I'm almost outta room...well,not in my opinion but my wife's.If it was up to me I'd line the whole house with tanks and throw out the furniture.All I need is a chair ~ I can just hold my beer in my hand.

Also my shed is lined with tanks 12'x12' shed.