my husband and I had the same problem. we got a brittle star and all he does is wrap around our rocks, so sand time at all. We also got about five red hermits and they may eat some of the left overs but they mainly stay on the rocks as well. Luckily both our eels and brakish lion dig up and stir up the sand enough to get most the gunk caught up in the skimmer. so i would recommend a bottom dwelling fish or eel