Living in an apt on the first floor has caused me to have many ants. It seems like as soon as it rains or the weather gets nice, here they all come. My landlord REFUSES to fix the door. It has a gap all the way around it so they just come on in whenever they want. Two years ago it was so bad that they were in the boxes of food in the cabinets. I had to throw away every piece of food in the house. To get rid of them we tried everything, even those sticky things. The Combat Houses don't work. The sticky things didn't work either. They got smart enough to walk around them, instead of across them. Finally I went to Lowe's and got ant spray and walked the outside of the house, spraying every little spot. Since you live on the third floor, you should try spraying the parameters of the house on the inside. There are many chemicals out there that are safe if they are eaten by animals. But, while spraying, cover your tank until the mist subsides. We got a chemical in a blue jug and it didn't stain the carpet, walls, tile, or counter tops. In fact, it completly disapeared and we never had ants again until I mopped the floor.