can some one help me please with a prob in me tank

hi all i got a prob with some thing growing in me tank



its not hair alge because it not like what i have seen on you tube vids



this is more like green storks it started with a few i pulled them out but more just came back



and now there is loads



i do weekly 40l water change plus 10l external filter every week

in my external filter i have phoshate remover and carbon



my tank has been set up since nov 2014

i got

4 fish

8 turbo snails

3 nass snail

and 2 red legged hermit grabs

20kg live rock

skimmer

led lights



its starting to do me head in any one got any ideas tia



john