I found one MTS in my 55 that had hitchhiked in on a plant. I thought he was cool so left him. He is about 3/4 inch right now and I see him and other little ones on the glass occasionally.
I found a very small one on the veggie clip when I removed it from the 55g, so put it into Pickles (betta) tank. I have done that 3 or 4 times, and now see them all scooting on the glass late in the evening, with Pickles watching them go.
I watched one bury itself into the substrate once (well you just realize it is going deeper, I couldn't see it moving) They can really go when they are on the glass. Their little tentacles are like little threads ...I love these guys!!
Val