I think the answer is ethos
In the second stanza, the poet describes the number of daffodils. ... 'I Wandered Lonely as a Cloud' is one of the most pleasing poem by William Wordsworth which illustrates the beautiful nature and how nature's beauty have the power to brighten up a person's mood.
Sergei considers the goldfish to be his friend. From the statement, it
is shown that Sergei has trust issues with other beings (May it be a human or
animal). He may have a dreadful experience in the past that prevents him from
befriending others. And he made an exception with the goldfish because he found
out that the goldfish will not leave him even if he is troubled.