What is my green bubble tip doing?

[Coach Vince]

Last night he was all spread out and happy, today I find this?

 

[Sugar Magnolia]

It might be getting ready to expel some waste.

 

[triscene]

When they digest, they are in position or maybe just some fish touched it

 

[Coach Vince]

Sorry should put in more details. I'm about to do a water test but my RBTA is loving life, everyone else is happy and the GBTA has been in my tank in the same sport for two weeks plus.