What is growing out of my mushroom?

[Mark Bradley]

Looks like a bubble. Is it part of the mushroom?

 

[AdamD76]

Looks like the mouth is poking out. It could be stress or something irritating it. Mine on occasion do it. Not a problem unless it continues for a more than a day or so.

 

[j.falk]

It looks stressed. Did you change something? I had this problem when I upped my lighting as well as when I would do large water changes...it would stress my mushrooms to where they all looked like this.

 

[Mark Bradley]

It looks like it is going to split into two - perhaps that is the issue?

 

[josephxsxn]

Reminds me of when my Hairy Mushrooms eat something like the random pellet that they managed to catch.