Alright, caught the snail again and put him in a small pyrex dish to try and snap better pictures. The letter x in pyrex is about 5mm tall (a bit over 3/16"). I didn't get a good picture of him directly against the letter, but I would say he is a bit smaller, so I'd say 4-5 mm. He very likely...
I thought lymnaeids were called pond snails instead of bladder snails. It doesn't match the description because mine has an operculum and lymnaeid lacks it. Mine also seems to have long slender tentacles. The temperature of my 10 gallon is also at 79*F which seems way too warm for lymnaeid to...