slugs in fuge eating macros?

[bridge man]

I've been having a hard time growing macro algae in my fuge and just recently I noticed some type of sea slug. They are on the macros and it seems as if they are eating them, not like a catepilar eating a leaf, but rather somehow killing the stems. I believe they came in on some prolifera from floridapets. If anyone has had experience with these things, your experience would be greatly appreciated. They look very similar to those in the picture half way down the page at http://www.pbs.org/wgbh/nova/algae/aliens.html
Thanks

 

[bang guy]

Here's a pic of one of mine.
They suck the fluid from the stems. I think they're inteesting but the population could easily get out of hand.

 

[bridge man]

Do you know of any way to get rid of these things? It appears as if they are gaining in numbers and my macros are losing the battle.

 

[bang guy]

shake the macro and net out the slugs. They don't hold on very well.