I have a piece of Redmoor root soaking - been soaking for about 2 weeks. Tannins are almost out and everything is fine EXCEPT for the fact there is a thin scum, sometimes tinged with small brown particles. The wood itself seems fine and no signs of any brown algae - water is not cloudy either. Is this natural? If not, what might it be and is it OK to finally place the wood in my tank when I start setting it up, (1st time I've used redmoor root). Thanks in advance.