They don't look like MTS' to me. MTS' shells some to points, these are just rounded at the ends. These are also much to fat and cylinder shape. All the MTS I have seem to have a little dome right at the end and then the cone goes down into the point and are colored light brown/white usually or some variation of there off. I could be entirely wrong, but having MTS' in all of my aquariums I'm pretty used to what they look like. As long as they don't munch on the plants though, I don't see what harm they can do, definately will give the puffer some fun.
Member #6 of the Eheim Pimp Club - 2 Eheim 2213 & 2215 w/ surface extractor, LiquidDoser and Auto Feeder.