I think, you go with whatever you like the look of. Mine is about 3.5 inches in some places and 5 in others. I like having a pistol shrimp because he changes the landscape and stirs my sand bed, so I don't have to (not that I would anyway). If I did not have a sand bed, I would not be able to have a pistol shrimp. But I also would not have to worry about what's in there as far as pests and detritus. I like a more natural looking tank so a sand bed is necessary, no matter how deep. Depending on your flow, some sand beds just get blown around. I like the look of a fine "sugar" sand, but it would not work in my tank. The choice is yours! You get to choose