How do you grind shrimp or other seafood to feed the corals?

[itelshot]

I usually give the corals finely chopped shrimp, but even these pieces are often to big, does anyone have any ideas how to grind it finer ?
I was also thinking about buying a mortar

 

[Dburr1014]

I have a blender and throw all kinds of food in there with tank water and freeze it.