Sourdough

Aaron began life, this morning, as 500g of warm, filtered water, 250g of King Arthur bread flour and 250g of King Arthur whole-wheat flour, but he doesn't look as liquid as the starter in the video. Should I stir in a little more water or just leave him alone?

One other question: in the video, you use what looks like a Lexan container and you say to cover it tightly with plastic wrap. Would it be okay to use a Tupperware container and its own lid?

Thanks!