I've got two of my new girls (right at 100 grams) in 15 quart tubs, and even those are a bit roomy for them. I just have two of the smallest plastic flower pot saucers in there for them and even those are big for them - but they're feeding, so it's all good!
The challenge of smaller tubs is finding hides small enough to fit AND a small enough water dish (at least for me).