Well Leo,A Cana alone gets a pretty decent size-the Brig will get to a size close to a Golfball when full grown. I think a couple Guppies (same sex) by the way,can give you something more to look at.As Sandy & Smack said,when full size,the Snails will really be the Max for the tank,so definately stick to two,and your best bet is to get the same sex,as I mentioned.The worse thing you could do is end up having a breeding pair,unless you're prepared to get another tank,they'll overun your tank in no time!