I have a Tunze 9005 and it is my first skimmes so I am still trying to figure skimmers out. I have the air valve open all the way and my bubble height continues to change. Right not it isn't even climbing up the column but the column is coated with a THICK nasty dark green odorous crap. I just started cycling last night so I assume there is a break-in period. But last night before I went to bed I had a good bubble column. What's going on?