A filet is usually around 1/2 lb right? Mandy, Nova, and Luka all get fed 3/4-1 lb a day, so a filet is usually fed with something else. You could feed kibble in the morning but I really wouldn't feed other raw stuff right now, except maybe chicken. You want to gradually introduce new things into their diet or they are going to have a major tummy upset.

If you do want to feed all raw one day, I would add chicken to it or if you have more fish then add that. Chicken is very bland and a good meat to start with, dogs usually don't have much problem with it.