That was an interesting article, thanks for posting it. Brought up some interesting points, especially about the differences in swimming needs of different fish.
This also brought up another important question that I haven't seen discussed. The amount of Live Rock, decorations, sand, plants, ornate rock, overflow boxes, etc... ANYTHING that takes up water volume in the tank. I've seen many videos/articles online of someone with a 200+ gal
tank, but who have it stocked to the brim with LR
, corals, powerheads, overflow boxes... and by the time you look at a profile of the tank, I would say there's less actual swimming room for big fish than a similar sized width & height tank, but around 12" deep front to back. I would look at this tank compared to a 140 +/- tank that is lightly stocked with LR
, and compare them very similarly in regards to actual room for the fish to swim. Albeit there would be more rock in the 200 to help filter the water, etc.
As I do think the Emperor Angel will be fine in the 140, I wonder if the few tankmates I've chosen to get in the near future will be suitable.