need help to id this
 

my brother has this growing in his tank:

http://i79.photobucket.com/albums/j1...1/idneeded.jpg


good? bad?

Nice...my rule is...if it grows slowly, in one place...it's good.

If it grows quickly, everywhere...it's bad.

Basically..if nutrients are there algae is going to grow. If you are lucky, you get to choose which algae grows. This one doesn't look too bad.

looks like dictyota to me, that would be bad.

That's weird...... It almost looks like a single color frogspawn.

To be honest, I see what looks like three different types of algae there. I say pull 'em. Better safe than sorry.

I see a couple different algae too. The stringy type algae left of the mass is bad. Not exactly sure what it is but its a PITA to pull off rocks. I would try and get rid of all of it.

I see caulerpa on the left, some sort of stringy junk in the middle and that other stuff not sure... it could be this?
http://images.google.ca/imgres?imgur...%26sa%3DN&um=1
http://images.google.ca/imgres?imgur...%26sa%3DN&um=1

If it is a "codium" it says it is very invasive... =/