Shite no! it's harmless, like I said the soda ash treatment will speed it up but thats just a one time refill. Redwood is loaded with tannin, thats what makes it resistant to rot and decay. Did you recieve any care instruction? Its also pretty sensetive to chlorine and bromine is a big no no!! Yes have the filter in if you do the soda ash treatment, I've done three redwood tubs for customers, the first one was a disaster until I found out about the soda ash treatment, the next two went great, customers were very happy and still are. It's just the nature of the beast, I learned from an old hippie from the sixties, by chance he lived two doors down from the first customer Once again if you want to speed it up add the soda ash to the existing water... then drain and fill.. start your water balancing and go from there, evetually you will filter out all the "tea" but it's really not a concern unless it gets a cloudy brown.
A quick google finds this site with lots of info and a start up routine:
http://www.xxxx.com/WoodTub_IonCare.html
EDIT, guess you cant post a link here, sorry, pm me or email if you still cant figure it out
Fish