Need suggestions on Blackened Perch

No advice but anxious to see the pix, ate many perch at the grandparents' house as a kid but never blackened.  

To blacken you need to get the cast iron as hot as you can. It doesn't matter what type of wood you use since it's only going to cook 60 to 90 seconds. It's important that your meat is room temperature since it won't be on long enough to cook the center. I know you want to be healthy but you need the butter, that's actually what blackens. Take your meat that's at room temperature and just before you throw it on brush it with melted butter, another reason for room temperature, you don't want the butter to congeal, then season it heavily. Cook the first side pull it repeat the butter and seasoning. This allows the cast iron to get hot again.  Good luck and have fun. Once you get it wired you'll try all kinds of things. Chicken, steak, pork chops. ....

These days, what "blackened" means to most people is just sautéed with "blackening" seasoning.  That's not what Paul Prudhomme did when he invented that technique.

I think you're right that the pan almost certainly wasn't as hot as Prudhomme's.  As I recall, he rolled the fish in butter, then seasonings, then threw it on a cast-iron skillet that was outrageously hot.  The result was CLOUDS of smoke, and he strongly warned anyone against ever attempting this inside unless you had a professional exhaust hood!  He said if you're a home cook, either do it outdoors, or don't do it at all, because if you do it right, there will be a LOT of smoke.  Here's a description of how he did it.