need some help with identifying this

[brokendeck]

We have two of these mysterious things in our tank. The pictures aren't great but they are as close as i can get without being completely blurry.
thanks for your help!

 

[cranberry]

Common name is pineapple sponge. Sycon.

 

[brokendeck]

a couple more

 

[brokendeck]

I assume they are okay to have?

 

[spanko]

Filter feeding sponge. No worries here. Probably come and go with available nutrients.

 

[brokendeck]

Thats good to know. Thanks guys.