Engine66,
I have tannin stained ponds and can find absolutely no problem associated with the tannins. A couple of my ponds are an estimated 70 years old. One pond has probably about 100 acres of heavily forested land that drains into it...and no problems whatsoever. The water that drains from this forest is tannin stained...so pumping the pond out to get "un-tannin" water would be an exercise in futility.
Are you concerned about aesthetics or some other problem?
