For years I was wondering why I could not keep MTSs alive in my 55 gal tank. I suspected for some time that either my L201s or my L199s are snail eaters but could never confirm it. I always find empty, chewed up MTS shells in this tank and the water values are no different than the ones in all my other tanks. I left the lights off today as I had to go in really early and did not want them on for 15 hours. So the plecos came out to play. I turned on the lights at 5 pm and saw one L201 happily munching on an MTS. Mystery solved. L201s are snail eaters.