First, it's illegal to shoot bass in most all states, including Texas. There are plenty of legal fish to shoot, don't get yourself in trouble.
Second, 30lbs is fine for most fish. You'll only be under-powered on reallybig fish in deep water. For most carp, gar and buffalo fish, you'll be fine.
Read this too...
http://www.huntingnet.com/articles/articles.aspx?articles_id=504
Texas has a great bowfishing organization, here's a link to it.
http://www.prismnet.com/~timmckee/