I was out two weeks for vacation and when I returned my 120 marine tank was literraly covered with long brown slimy alge, not a single rock escaped. a huge outburst - it's really ugly and long! I've never seen anything like this in all my years in the hobby. A friend of mine took care of the aquarium while I was gone - but he did this for me many times over the years - never had issues before. I can't figure out what on earth caused such slimly growth in only 2 weeks. Any idea - and more important - how to get my aquarium back to normal?