Re: "vegan fish"
Hardly surprising - cats are pure carnivores. Amongst other things, they don't have the ability to create taurine
Fun fact one: tuna meat contains almost no taurine. So if you see a bargain on tinned tuna and buy caseloads figuring to save on cat food, your cat is fucked. It's usually the heart and retinas that suffer irreversible damage, and the heart damage can lead to death.
Everybody with a cat is going to point out that you can get tuna-flavour cat food, so I must be wrong.
Fun fact two: on those cat foods that list the ingredients, the flavour ingredient (beef, chicken, tuna, rabbit or whatever) is present at around 4%. Enough that when you open the can it smells vaguely of the flavour. For all I know it may even taste vaguely like it. The rest of the protein is anonymous, but makes up for the lack of taurine in the 4% tuna.
Fun fact three: Aldi chew sticks for cats, such as Chicken and Liver, contain 16% of each of the flavours. So 16% chicken, 16% liver. Which might explain why, if you can persuade your cat to eat the first one, it is likely to go mad for the things.
Fun fact four: the Aldi chew sticks don't have a strong aroma. But what there is remains trapped in the wrapper, so scrunch the wrapper under the cat's nose as you squeeze the stick out. That will often persuade a cat that it really is edible.
Fun fact five: the Aldi chew sticks are significantly cheaper than the Tesco "cheap shit" ones, which are significantly cheaper than the Tesco "own brand" ones, which are significantly cheaper than the "big name" ones.