Like Sol and Jay said.. nothing to be overly worried about, but 99% of the time a symptom of over-feeding/inadequete solid removal. I found feeding small amounts to my fish frequently and water changes more frequent then not keep them in check in my system. Not much kills them chemical wise, and your more likely to harm your gars before killing them off. I had an issue with them briefly i think 2 yrs ago where food had been trapped and was rotting and caused an explosion in numbers. a few big water changes to remove as many as possible, and switching from feeding a ton in one sitting to 2 small meals ( what the fish would eat in 5 mins) got them under control within a week. iir I did 75% wcs every other day for that week, and rinsed out my filter media to dislodge any hiding in it. not to mention removed the decor that trapped the food to begin with and scrubbed it down with an old toothbrush really well.