What is this yellowish blob

[TinaFoster]

Is it some sort of sponge or tunicate maybe?

 

[cloak]

If it's not moving around then my guess would be some sort of Tunicate as well.

http://www.saltcorner.com/AquariumLibrary/browsesectiongroups.php?SectionID=36

 

[TinaFoster]

Way cool, but bummer that it probably won't be around long. Thanks!

 

[TinaFoster]

Well it's changed and raised up a volcano looking hole.

 

[Squishie89]

95% sure those are tunicates, very cool animals, can be hard to keep unfortunately.