If the fuge is connected to the same tank the detritus came out of then it is not necessary or desirable to put any in your fuge, plenty of detritus suspended in the water column will be going in your fuge carrying with it whatever bacteria etc you would be adding, you'd just be putting an instant nutrient sink in your fuge. If the detritus is from a tank not connected, just a tablespoon or less will add bacteria etc if that is what you are after, they multiply exponentially...