"Moja ryba je chleb."

Translation: My fish is eating bread.

[Lahnuska]

Lilo's weather fish...? :)

[Kashakot]

To jest moja ryba.
Moja ryba ma na imie Pudge.
On lubi kanapki.

[Jellei]

Well, "ryba" is feminine, so "on" doesn't seem right here ;) If the given fish is male, then maaaaybe... but frankly, the best option is to just omit the pronoun. The subject was stated a moment earlier, it's still clear in the third sentence what the subject is, you don't have to put any explicitly.

In Nominative, you rather don't use pronouns (on/ona/ono) to refer to anything other than people. Sure, if anything, than for animals, but even if it's not technically wrong, then it's at least strange.

[Chris_Rzech]

Woahhh. She spoke really quickly

[centaurii]

That really did not sound like the usual voicing of "ryba" so I was thrown off. Is it pronounced differently in some sentences than others?

[Jellei]

It seems okay to me. When you know how different letters are pronounced in Polish, then you know the pronunciation of 99,9% of words, there are virtually no surprises. It really shouldn't be pronounced differently in different sentences.