Selcon is just a vitamin, there are several, Kent Zoe, Ocean Nutrition Vit A Boost, to name a few. The key is good nutritious seafood in your recipe (not previously cooked, etc.)
I have a recipe I have used over two years (and modify constantly) on my website. I do add vitamins as you mention...usually also on the cubes as they thaw, as they seem to have an attractant, (or else the fish just really like the food..)
There was just a good thread with some some good recipes.....
JMO and HTH