i acctually used to have a rubber one. it was a T-Rex that came in an egg.
you put the egg in water and i breaks free and grows. It did have a ton of slim on it once it grew. kinda simalar to a fish's slime coating.
Well since its just my betta I actually am gonna get a 3 gallon tank (its in my room so I cant get it any bigger) so I'm gonna get rid of my silk plant and get a real one and a little cave hidding place with a heater and I think my fishy will be MUCH happier