iron issues?

Hi guys. I just saw this piece of aquatic wood and was wondering what was going on? Is it the oxidising of the iron in the wood? …I may of just sounded like a complete idiot. Thanks guys as always.

Hi All, This is my first post but i have been lurking around the forum for some time. I'm hopping to get some advice from some plant experts. Tank Specs. 129 lt tank (100 lt of water after sub etc) 35 watt fluval plant grow leds light on for around 8 hours Just started e.i dosing. Pressured...