How do you get rid of ants in your hot tub?

Question

One day the water inside of our hot tub was filled with dead ants. We cleaned out the filters and scooped out the ants and thought that would be the end of it. For the next few days it seemed ant free, but if we don't use it for a while the ants are always back. I don't know how or why the keep getting in to drown themselves.

Answer 1

place coffee grounds around the base of tub.  

Answer 2

This is the most wonderful discovery, the heaven sent answer to many peoples problem. Patent it quick. Call it the ant exterminator deluxe, on the other hand these could be "Lemming Ants"  

Answer 3

Terro works like a charm in the liquid form.

I use it sucessfully every time I have an ant problem.