Hi, I use a gravel vac to clean up after my 11" Common Pleco. That way you can clean up between water changes if you don't like the look of poo all over the place, which I don't either!
What size tank is he in? I agree my pleco poops strings of poop all over the place and sometimes I will find long strings of poop stuck to the intake of the filter.
I had a 16" pleco that would have a rope of detritus 2 - 3 times its length trailng it. I had to chop it off with the gravel vac at times. It wouldn't suck up if it was still attached.