I personally dont like X-High tanks. They have very limited surface area for gas exchange because they are so tall. With the limited gas exchange for example an Xtra tall 80 probably has the surface area of a 55 gal
tank or something simular. So in reality even though its an 80 gal
tank you should still base your tank capacity as if it was a 55 gal
because the suface area is no greater.
Not to mention tanks deeper than 24" can be a real PITA to maintain cause the bottom is so deep.