This has been covered before, so for the newbies;
As Chef Ramsey points out, it is cheaper, tastes better and is healthier to make your own foods. This includes fish foods. I have been doing it for a while now and I can tell you it works. No disease, much less fighting and pretty fat fish. My tangs are all very meaty.
Buy nori sheets from a Chinese food store or on Amazon. Used for sushi, it is cheap and they love it. You can even grind some of this up and add to the below;
Make the following, feel free to use alternate ingredients, as long as its seafood. No chicken, or roast beef...
Can of oysters, drain
Some white fish, or salmon even can work, no bones
Some shrimp, cooked or uncooked.
Add vitamins and some garlic extract and some RO
Let sit in refrigerator overnight to absorb the vitamins and garlic.
Then put into food processor, or mince with knife into a mash. Put the mash in some cheese cloth, or clean dish towel and squeeze as much water as you can to make a kind of fish dough. Divide this up into freezer bags and smash into flat sheets before freezing.
The fish will try to kill each other to get to this mixture.