The friendliest place on the web for anyone with an interest in aquariums or fish keeping!
If you have answers, please help by responding to the unanswered posts.
Difficult to see from the pics but yeah could easily be a sponge. I had a similar White / clear looking branch which I believe was a sponge, that's sort of what I'm seeing in your pics. I really don't think it's anything to worry about!