Several years ago ,a study was published in Coral Magazine. Popular frozen food brands were tested for vibrio bacteria. All presented vibrio bacteria even with a continuously frozen chain of custody. Whether these bacteia would harm the animals in our tanks is debatable. Nonetheless, the researchers recommended a soak and rinse in clorinated tap water before use.
It also seems the packing water used for many frozen foods is nutrient laden, so draining it off makes sense.imo..
I use about 2 oz of a mix of mysis ,brine, bloodworms and cyclopeeze each day along with some flake and nori. Aluminum foil wrapped 4oz packets( 2 days worth ) are measured out and stored in the freezer every 3 weeks or so. The frozen chunk is dropped in a plastic coffee can full oftap water and allowed to thaw. Then it is poured through a fine mesh net( brine shrimp net). The food is dumped back into the coffee can and ro water is added. This 2 day mix is fed with a small turkey baster and kept in the refrigerator.