Does anyone know what this stuff is? There is black spots all over my plastic and tank decorations. They apperaed only recently and now are spreading. I have no idea what it is? If someone knows what this stuff is, how do clean it??
once it starts it may be hard to stop...you can remove your decorations and clean them and use algae scrubber on the glass of you tank ( make sure your tank is glass )
do a serach in the forums for "algae" and I am sure you will find all kinds of things that will help with your problem...
also on a side note give some details on your tank ( size/filter/real plants/fake plants/ fish types )
one last thing if you tank is decent size look for a bristle nose pleco...they eat algae and will be a good start in stopping your problem..