I don't understand what kind of tub you are talking about. How big is it? Is it like a big plastic storage box? If so I don't see why not. I don't think the plastic is toxic but I'd look into that online. It will need a lot of ventilation. Is it clear? I don't think a piggie would do best if it is dark and covered all the time. Is it going to be in the box most of the day or out? I suppose you could set it up just like any other cage and a guinea pig would have just as good a life as it would in a glass or wire cage.