What are you feeding? If it's pieces of frozen cubes (mysis, brine, etc), do you rinse it? If not, then that "cloudy soup" is also adding large amounts of nutrients. I use a very small plastic cup (jello shot cup) to thaw my food, then pull the "soup" off with a pipette..... add some more water, swirl around, repeat. I do this about 3-4 times. I also spot feed a few bits at a time with the pipette, I don't just dump the bowl in. That way I can see exactly what everyone is eating.
EDIT: Are you using RODI