Can I get drift wood at the pet store?
Yes, you can. I bought a piece for my pleco for about $5, I think, and it was pretty cool looking, too.

Fish do grow slower in a small tank, but they do continue to grow. I personally think it is better to get them a larger tank and let them reach a more natural size, than to keep them in a tank too small for them and stunt their development. Some fish we normally think of as "small" aren't really meant to be small at all. Common feeder goldfish, for example, can reach HUGE sizes, if allowed to live and grow naturally.

My pleco's name was Pete.