@freemo Have you tried unagi sauce with freshwater eel? Here's a decent recipe, it goes with multiple types of fish, but is the best with eel.
https://www.justonecookbook.com/unagi-sauce-2/
I'd be careful with the sugar, and add it to taste, because it tends to be a bit too sweet IMO.
(I'm not asian, but my uncle is a chef from southern China, so I was spoiled as a child and never looked back lmao)
@johnabs I dont know how to make it but I've tried it, and eel with unagi sauce is actually one of my favorites!!! Thats a wonderful suggestion. I never cooked eel either and I might just want to give that a go. I was going to do mackrel is has a bit of an oily quality along the lines of eel so it would likely work well for both.
I'm not a fan of anything too sweet, I'll likely go minimal on the sugar, especially since im going for healthy here.
Also thinking of winging it with a soy, ginger, sesame sauce of some kind.. maybe just throw three ingredients might not need much of anything else.