I can't say I got rid of them completely but they are not near the problem they were a few weeks ago. I tried ant bait, the little tins, the ants avoided them. I tried DE along the the deck in the crack around the outside of the pool which helped somewhat but not good enough. I know of nothing to put in the water, I just keep skimming them out. They probably live in the dirt under my concrete deck.
I did an internet search on killing ants and came up with lots of BORAX recipes to kill ants. I tried a home-made remedy and saw some action. BORAX, yes "twenty mule team", the same stuff talked about on this forum! The trick is to limit the BORAX to about 1-5% in a solution of water thickened with something sweet to attract the ants. (I used about 1tsp BORAX to 1cup water) Boil the water first to dissolve the borax in it, then add honey or jelly or whatever you have, I used grape jelly to thickin the solution. Put it in something shallow like upside down can lids and put in the ant trails on your deck, I assume you see ants there to.
The trick is to use a dilute enough concoction that the worker ants can carry it home to their queens so it kills the queens to. But not so concentrated that it kills the workers before they can carry it home to the queens.
If your worried about pets or wildlife getting in to it, just cut some small holes in an empty coffee can with a lid and put your concoction in that. It's not really that toxic to animals though. I actually poured small amounts into the cracks betweeen the concrete sections and the ants found it easily there and went nuts for it.
It took a while before the ants were interested in it at all but after moving it around they eventually went for it. When they finally do, don't be surprised if you see even more ants untill suddenly one day they will almost be gone.
It depends what kind of ants you have, I had big black ones and then little red ones. It's definitely worth a try, cheap and it's good to have BORAX on hand for the pool to increase pH if you ever need to.
Good luck, I hope you find a solution! I would not actually put anything in the water, easier to just skim and bag ants out then to risk major water issures!