Theres actually a similar story with the fish. From Memory Alpha:

According to Ronny Cox, Patrick Stewart hated Livingston’s presence in the ready room, and constantly petitioned the producers to remove the fish. Stewart, a strong animal rights advocate who opposes many forms of pet ownership, felt that using a captive animal in an ornamental display was “immoral” and inconsistent with TNG’s core theme of exploring the inherent dignity of different species across the galaxy. Cox, who called Stewart’s point “well taken”, stated that Livingston’s temporary removal in “Chain of Command” was thus a “sort of a bone they threw to Patrick”.