Fish isn't as important as which part of the fish you're using. Fish heads and fins are ideal. Some people throw the skin and spine in there too, but in my opinion all you really need are fish heads.

Mackerel bones worked extremely well for me. Most of the bones completely disolved - fantastic stuff, and potent.

according to Nourishing Traditions by sally fallon the fish you should be no oily such as sole, snapper, rockfish or turbot, it is believed that the fat in oily fish could become rancid, and to cook the broth as little as 4 hours up to 24 hours.

Lean white fish like sole, St. Pierre (John Dory), Rascasse and the like. Make sure your remove the gills and possibly the eyes. Don't let your broth go too long, 30-45 minutes is fine.

I'm going to make my first fish bone broth this weekend I am going to use a snapper head and I'm going to throw some oysters and clams in as well.

Any kind of fish HEAD would be good.

I have heard not to do it with oily fish too, i of course tried it anyway. I used used two salmon heads (gills removed) & two mackerel spines, chucked them in my crockpot for 8 hours, strained them, me & my 8 year old got a bit brave & ate the fish salmon eyes & voila! lovely silky fish broth, it started to gel as it cooled on my worktop, im in no doubt it would have resembled a bowl of jelly/jell-o after refrigeration. I added prawns & some smoked salmon, it was epic! ive made it another two times with the same results, i have never tried it with white fish.