usually it's a pound to a pound and a half per gallon
are you planning on live rock or dry base rock because there's a big price difference
either way i'd start with around 30 pounds and you could always add more later
it all depends on the way you scape your rock work
remember you want your fish to be able to swim at all levels
in my 37 bowfront i left a 4inch beach around the front of the tank along with 3 inch on the sides
this is my fowlr my fish are hiding this tank has around 65lbs of rock some real porous
and light this rock you get more per pound
and some that's non porous it weighs a lot more and you get less per pound
i plan on doing lots of macro algae growing off the rocks
are you planning on live rock or dry base rock because there's a big price difference
either way i'd start with around 30 pounds and you could always add more later
it all depends on the way you scape your rock work
remember you want your fish to be able to swim at all levels
in my 37 bowfront i left a 4inch beach around the front of the tank along with 3 inch on the sides
this is my fowlr my fish are hiding this tank has around 65lbs of rock some real porous
and light this rock you get more per pound
and some that's non porous it weighs a lot more and you get less per pound
i plan on doing lots of macro algae growing off the rocks