My guys are in a decently planted tank so the poo is generally left undisturbed because the plants will benefit a bit. If the poo has accumulated too much then I just kind of stir the water up before I start suctioning. The stirring gets at least a bit of the debris up in the water column. Then I just suction holding the end of the hose nearer to the surface of the water to avoid the shrimp, the hose should pic up some of the stirred up debris.