bristle worm behavior

[Alberta-newb]

watched some interesting activity last night and quickly grabbed my camera...sorry for the lousy focus ( I was in a rush and still haven't figured out how to get decent tank shots)



Anyway, this worm took a long reach from the rock and started snacking on the film of hair algae on the back glass of my tank. It actually mowed it right down to the glass surface and the next morning I could clearly see the 6" to 7" zig zag pattern he left as he ate..and I thought they were so bad I think it may be because the algae is old and dying off (new set-up) and it has trapped a lot of detritus in it.

BTW, this guy must be about 10" long as the rock is a least a 6" reach to the back!