Fresh Water Tank Growths

[Bobsyouruncle]

Have a 10 gal tank set up for my grandson.   There are what looks like little dark plants growing on the tank decorations.
 
Have any Idea what this is, what I can do to get rid of it and what I can do to prevent it?

 

[carpking]

sounds like black beard algee not sure on the best way of how to get rid but ive read having pleanty of flow in the tank helps.

 

[eaglesaquarium]

Try this link to ID and combat the algae.