I picked up a simple fish taco marinade recipe from someone at Spearboard 1-2 years ago, and finally tried it today on some leftover halibut filets. I added a few things to improve it. It's quick and tastes pretty good.

Ingredients:

1/4 cup canola oil
1 lime (juiced)
1 tablespoon ancho chili powder
1 small jalapeno (finely diced)
1/4 cup diced fresh cilantro
1-2 teaspoons salt
1/4 cup diced red onion
1 clove of crushed fresh garlic

Mix all of these ingredients together in a bowl, and then pour the mixture into a large ziplock bag with skinned fish filets. Let the filets marinate for 1-2 hours. Grill them on medium-high heat. You can oil the grill before placing the filets, but I find that the oil in the marinade is enough to keep the filets from sticking to the grill. Hope you enjoy it. My family liked it better than the store-bought fajita marinade.

If any of you discover any improvements to this basic recipe, please post them.

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"At least the captain of the Titanic tried to miss the iceberg. Congressional Democrats aimed right for it."
-Scott Rasmussen, 2010

I add some Luzianna or Tony Chachere's spice on mine instead of using peppers. Then make a white sauce with some sour cream, miracle whip, garlic salt, some hot sauce, and lime juice.