[reefmutt]

If you go with the 8x3, you may never need an upgrade!
8x3 is a major build however.. wouldn’t be a problem putting all equipment underneath with that footprint... but then, all the noise that goes with it is right there.. lots of pre build work and lots of build work on a system that large.
The media room build certainly gives you the ability to make it quiet which is probably a necessity in that location...And the opportunity for the basement expansion down the road.. which would not require structural work to your home.
I have preteen and teenage hockey/soccer/lacrosse/basketball etc playing girls and my tank is in the same playroom as all of their indoor play stuff. There has not been any mishaps.. although, even though they are active they are not boys, who by nature are more nutso during play than girls..
I have no idea of your experience level but maybe the smaller build would be a good stepping stone to bigger things when the kids are bigger..
Sure is nice to have fish room. Not only for you but for the wife, so that all the paraphanelia can be hidden.. I just realized I have no idea how to spell paraphanelia.. and neither does the autocorrect on my phone..
Anyways.. to minimize the overall scope of the project, I say media room..
But if scope and money don’t scare you, go for family room.