Question: How much sand do I need?

[Lemi]

I'm getting a 75 gallon US. It is48 inches long, 18 inches wide which I believe is 120cm by 45cm.
Any brands or types you would recommend?
I also heard sand is somehow bad for their gills. I've used it before with no ill effects, but I am wondering if someone has heard the same and if there's any truth whatsoever to this.

 

[Kaysie]

Sand is fine, as long as it's not calci-sand or marine sand. It must be aquarium safe. Many people use play sand (which is fine-grained) or pool filter sand (a little coarser).

You don't need a thick layer, so 20 pounds of sand should be more than plenty.