Big and small red ear slider turtle

Question
Is it really ok to put a baby red ear slider with another big red ear slider turtle(3x bigger then the baby)? And whats with strange behavior that looks like the big one is trying to slap my baby one?

Answer
I would not recommend it unless the habitat is really big- Red-ears are territorial and larger ones will bully or block their access to food or good places in the tank.

One way a turtle harasses other turtles is to fake-court them- stroking their face with their claws- like a mating male would do to a female. Sort of like your turtle seems to be doing.

Try http://www.redearslider.com for good information.