Ants in containers can be challenging to control. If you are able, submerge the whole root ball of the plant in a bucked of water and that will flush them out of the container and you can get rid of them that way. If you summer plants outdoors, ants often will move into the containers to make nests. When the plants come back in for the winter they become active looking for food. There are some natural controls like wiping the surfaces with white vinegar to deter the ant invaders from returning. The houseplants might not be the source of the pesky ants but it is difficult to say without some more information. Sometimes there are insects like scale that secretes a sticky substance and ants are attracted. Remove stationary scale bumps with a wet paper towel on the plant, check under leaves and on stems. 

Hope this helps.

Courtesy of the NYBG Plant Information Service