there is no tuna i have seen ever that doesn't have salt in it. i just drain it off. my cat drinks a lot of water, i assume that the salt makes him more thirsty.
compared to the other options i have available at my local supermarket, it's the best. i do try to mix it up a bit sometimes with beef and also now with cod, i should pull some cod steaks out of the freezer to cook up for him to eat.
i think tuna is pretty good though, i mean, if his condition and health are any condition, it's giving him more than enough, and better than what any "cat food" is giving him (they make his hair manky and his allergies and susceptibility to parasites increases - this is why i stopped feeding them to him. and he now refuses to eat those things).
idk if you knew this but most cat food products you can buy at regular supermarkets are part or more than half composed of textured vegetable protein. i was raised on this garbage and i know exactly what it looks and smells like. my cat does not like soy. soy is not cat food. it's not human food either, but that's a separate issue.