what are these??

[frakes]

these popped up a few weeks after i added stuff to my aquarium, and they seem to cluster around each other... the largest is almost an inch long... i dont know if i should be worried or not

 

[1snapple]

Not sure, we had some on our new LR.
Hermits went to work and they is all gone.
Can't say if they are good or bad.

 

[slice]

It looks like a pineapple sponge to me, a harmless filter feeder.
I used to have 100s of them, but I haven't seen any lately.
Most folk have them soon after the tank gets going, most die out in time.
Take a look here, scroll down to the "sessile" category
http://www.lionfishlair.com/hitchhiker/hitchhiker.shtml

 

[spanko]

You got it Slice.
Scypha or Sycon sponge.
Pineapple or Q-tip common names.
Like he said harmless and will disappear over time.

 

[monsinour]

mine disapeard from the DT and ended up in my overflow box.

 

[spanko]

They are a sponge, they love the dark areas in the tank, cryptic areas. They are also an indication that you watertank has enough nutrient in the water column to support them.