This is a ? Regarding OBDII Reader's & OBDII CODES

What is your question?

My OBDII reader was showing me 2 lights, both of which I fixed. I'm new however to using an OBDII reader, would I then have to reset the codes on my reader or should it automatically see that I corrected the issue & not show up on the reader anymore once fixed? For instance my codes had to do with the cooling system. The previous owner apparently mixed 2 different coolants together which led to a clogged mess, my codes had to do with the thermostat & some other part of the cooling system pretty certainly having to do with the gooey mess I had to blow out through the whole system I can't remember the specific #'s off the top of my head but I replaced the entire thermostat & housing blew out the entire coolant system & my OBDII Reader still shows the same CODES but I'm certain I've resolved the issues. Do you normally have to reset the codes on a reader after fixing it or should the reader recognize the issues have been resolved on its own? Thanks for any help you can offer me.