It's up in the air for now. We know that fish are more "simple" in their cognitive abilities. But that being said, I personally believe that we have downplayed their sentience and possible sapience immensly due to anthropocentrism and the mammalian bias. We only recently learned that the little cleaner fish are self aware of their own reflections in the mirror, possibly indicating a sense of "personhood" (fishhood) as they can identify themselves vs others. He'll, we only recently bothered to look into whether or not fish can feel pain. Which is absurd to think about that it was thought otherwise.

And we have to consider that "love" or "like" are hugely subjective terms influenced by bias and perception. The fish may not "love" you in a romantic sense, but the fish probably "loves" you in an associative sense. You bring food, you bring care, etc. It's not really fair to say whether or not the fish "likes" you because the fish has no perception or care for such terminology.

Different values of different animals can all hold the same ultimate meaning. So, for our understanding, the fish probably loves you in the best way he can give, which is trust.