I recently lost 2 angels to an attack (most possibly from my catfish), as no one seems to believe that my silver dollars are capable. While removing the dead fish i noticed that 2 big lumps of wood that i had recently added to the tank looked like tea bags in that there was a brownish colour leaking from them. I removed the wood , however, i now have what looks like an oily grey film on top of the water and the water has become very mirky, not bubbly or cloudy but just mirky, i did a big water change and nothing happened. I have 2 filters running ...any ideas what this could be.?