Sounds good, thank you!Yes Apisto's would be fine with your current fish. They can be a bit territorial durning breeding and will warn your cories off but no real harm should come from it. (*if you do want to breed them they would be best in a tank on their own. The cories would devour the apisto eggs)
Id go with just a pair in a 29g. I had a trio in a 22g long which is 90cm in lenght but had a few issues with them getting along. Their in a 55g now and are much happier.