Please Help ID Growth in my Tank!!!!

[rlopez8]

I have a white fuzzy growth in my 75 Gal saltwater tank. Can someone please ID this for me??? Thank you!!!

 

[jtodd315]

I have the same thing but it only grows in my sump on my Weirs I think it's some kind of sponge they were growing more when my phosphates where high and I was over feeding my tank after I lowered my phosphate levels and started dosing Mg to help with my algae and Ca absorption they started to disappear may have had more to do with the high nutrients

 

[bang guy]

Sycon Sponges AKA Q-Tip Sponge

 

[rlopez8]

thank you so much! It seems as if they are harmless from what I read. Is that right? They are spreading a lot. How can I slow them down? Thanks!