Is "Your fish is fat." wrong? In German we use is (ist) evenif you have a lot of fish.
Both "pisces" and "fish" can mean a fish or many fish but the verb is "sunt", which is plural and must be translated "are".
"Both "pisces" and "fish" can mean a fish or many fish..." That is not correct. "Pisces" is Nom Pl = many fish, so you have to use sunt in the Latin sentence, which is totally correct and clear. The question I have, affects the English translation. The question I have, is the English translation. Does "The fish is fat" mean you have exactly one fish or could it also mean that you have many fish.
It can only mean that you have 1 fish. In English, fish is an irregular plural. That is "1 fish is..." But "2 fish are..." The verb will show the singilar or plural.