Most of cooking housewives should have a food processor. Or you can go to any stores selling cookware. I can't think of any national chain store now as my brain is dead right now being a southern californian waking up early in 50F room. My heater broke............
As for salmon, any thing is fine as long as the meat is not dehydrated (freezer burn, for example), relatively fresh. You can get them at any supermatket. To supplement it, add some shrimps, freshly shucked clam meat, and a couple leaves of spinach. You may need to add a few tsp of water to make it easier for your food processor to chop.
After everything comes to a consistency of your choice, place the glob into a zip lock bag. flatten it to get most of the air out. Freeze it. Break out a small piece to feed your fish as needed. Seafood like this is relished by most fish and corals in your tank.
