from the photo looks like you don't have the plants deep enough that could be why they keep tipping over... if your going to grow pineapple plants in pots you should stake them up with some bamboo..... and only time ants are a problem with pineapple plants is if the plant has mealybugs and from the photos i didn't see any mealybugs..... to help get rid of the ants try putting some diatomaceous earth on the top of the soil.... it has to be dry for it to work to kill the ants.... and i meant to say ant's wont hurt the plants its mealybugs you need to worry about that's mostly why ants would be on or living in a pineapple plant or soil