Limitations of Depth/Shallow Reefs

[Cell]

You need at least 'x' gallons and 'y' feet of tank for 'z' fish. Rarely is depth accounted for. What are the livestock limitations of a 16" height tank? For instance, can a theoretical 6ft, 150 gallon 16" height tank house happy tangs or do they need more vertical swim room? What if you add a sandbed and now only have 13-14"?

 

[Hydrored]

I have an 8’ 21 tall lagoon style and the only fish that spend any time on the top 1/4 of the tank is Anthias and chromis. Large fox face and tang does swim the whole 8’ all day long. Once I doubled the length of my old tank all aggression went away. I feel there is truth to having more swim space length wise for healthier fish

 

[Cell]

I wonder if that top 1/4 of empty space is needed though for some fish to feel comfortable.

Isn't 21" a bit deep to be considered a lagoon?

 

[Hydrored]

It’s pretty shallow once you consider the water height, rock space with caves for fish, etc. I guess you have a valid point but I would not want any lower to allow for rock scape and coral growth that’s for sure.