For 4-legged creatures, I use a pressure cooker. That it turns gelatinous in the fridge is what I look for. For fish bones, I just use a pot on top of the stove. Neither tastes like commercial because I don't salt it until I eat it as soup or use it in a recipe. I also use a couple of tablespoons of ACV in both to leach out the minerals from the bones per primal guidelines.
The broth from beef/bison/goat comes out a bit darker than the one from fish bones/shrimp heads, but not as dark as anything I ever bought from a grocery store.