Research widely suggests this increases risk of prostate cancer in men. Just so you know. You probably shouldn't take any.
The normal expression in English is "fish oil", not ever "fish's oil" for the generic case. If you wanted to speak about the oil of a particular fish, only then you might say, "the oil from this fish is good" or "this fish's oil is good". And that would also have a different equivalent in Spanish, e.g. "el aceite de este pescado es bueno".
How is "bueno" interpreted in this sentence? Good - tasty - It will enhance your piella. Good for purpose - It will work. Good for you. - It is full of vitamins. Good to go - It doesn't smell off or rancid. All? Different? Are there other, more specific, ways to say this? Thanks!