Terrarium size.

Ok so i originally bought 2 hognoses 1 male one female and all the suppi4s and tanks. (they ship on tues ) then i was looking on his website and fell in love with another female he had for sale. My question is would i be able to put one in a 40 gal front opening tank. They are all around 20 grams. Or should i go out and buy another tank. I just have the 40 gal sitting here already .