Just got back helping to take care of my friend's kids (they are such a handful!) and then walked over to my LFS
They had their 20% off sale almost everything (10% off the tanks/stands) and for ever $10 we spend, we got a raffle ticket to win either Gift Certs at their place or $100 Best Buy card :P
Anyway, I started talking to the guy and he said 40G should be fine but he said he's not going to tell me how I should spend my money.
He talked about 3 systems that are out there for SW
systems, one of them was a refugium, another was the sump system, and a "Berlin" system. It's all news to be and he said the Berlin system was the quietest. Some other system sounds like a "toilet"
He also mentioned a 40G with a built in overflow and sump would be better. I wasn't sure what an overflow does yet but i think I'll be doing a lot of research.
In addition, maybe I will go for the 100G. He said he has a 90G on his 2nd floor (and can go even more in gallons) and that's where a lot of the weight can be supported anyway (our house was built in 2001 so I assume it was done to meet building codes....)
40G tank? probably 4-5 fish depending on the fish.
50G tank? the most popular size they sell. Should be fine for SW
He also has a 55G which has more depth and not as narrow 36x18x20
(for his home).
They have a NICE 180G. I wonder if I can do that on the 2nd floor