Dumb question

[Mordie101]

So when people say “x” fish needs 180 gallon tank, is that referring to display tank size or total water volume? Red Sea reefer does tanks that are 200 gallons but display tank gallons says 160 gallons with the sump being 40 gallons.. I’m trying to build my dream tank and trying to get a good tank for all the fish.

 

[mich2599]

Tank size as they will grow big and need lots of swimming space.