Do you have hiding places for your octopus? If you can see him when he hides, he needs a better place. Good hiding places will help with the jetting. What size is your tank?
Oh, I see you posted the tank size while I typed. Yes 60 cm long is too small for vulgaris. The tank should be at least 4x longer than the animal.
Unfortunately,I can't afford a larger tank yet，as a student.I got a jar for him，but actually he sleep inside few times，maybe a jar is not suit for
variabilis.My tank is 60*60*60
Maybe I can free a vulgaris when it grow up.But before that，more problems should be solved to keep a vulgaris alive.They die easily,by the way it's nice to talk with you, please give more suggestions on vulgaris later when I get one.I will be very appreciated.