Thank you for everyone’s help.
I have some aquarium salt on hand, now is when i start asking silly questions as i’m unsure on how to go about this.
So, although the pleco is in quarantine, the water in the box is just filtering through from the tank so i’m right to just add the salt (and medication when i get it) into the whole tank? Then do a good water change in 5 days
I’ve had my fish a while but never had to quarantine, so i apologise for the questions!