I have 4 in my 10 gal tank & about 7 in my 55 gal tank. I think they are about a couple of inches long. I love em!! They are fasinating to watch, especially at feed time, they are the first up for food, they grab it in all their "paws"( lol) then hide to eat it.
mine does the same, sadly i only have the one, brought just 1 to try with my betta girls not found any again since, but hes always out exploring, they are just the funniest when feeding, mine does the same thing