I recently asked a similar question as I added some MTS to a goldfish tank. I got an answer something along the lines of if he can get it in his mouth, t can get through his digestive track. So there shouldn't be any worry about him hurting himself eating any MTS.
I'm hoping my goldfish has learned to NOT eat MTS. Within hours I saw the goldfish suck up one of these MTS. Apparently he didn't notice the juicy inside part and only noticed the hard shell and spit it back out. So I'm hoping he won't try that again. At least I have not seen him trying to eat any more large ones. As for small ones, well I have not had the MTS long enough to determine if the babies can survive. Apparently it's somewhat possible, because sifting my old sand after moving the goldfish from a 10 to a 20 gallon tank, I found at least three baby snails.