**whispers in ear** Frooooontooooooosaaaaaaa.....
Depending on what size colony you want, you could potentially house them for life. Or you could upgrade many years down the road, as they are super slow growers (plus then you can start again with new stock(lionfish) in the 125
). I have 5 fronts in my 150, ranging from 4-9 inches or so. The youngest is 1 1/2 years, who I had since a baby, the others I'm not sure on age, as I have acquired them over the last 2 years. Eventually it will be just them alone, and I plan to breed them.
Depending on what size colony you want, you could potentially house them for life. Or you could upgrade many years down the road, as they are super slow growers (plus then you can start again with new stock(lionfish) in the 125