so these aren't just black ants, they're biters!

There are several commercial preparations to kill ants, but I use borax. They carry it back to their nest, and it kills off the whole colony. Unfortunately, with any treatment, a new colony often shows up.

Borax ant poison for sugar-loving ants: mix approximately equal parts borax laundry additive (or boric acid, or roach-pruf) with sugar, then add enough water to make a paste.

If you skip the water, the ants will take every grain of sugar and leave the borax.

Put the paste in small containers, like jar lids, directly on ant trails if possible. Protect from rain if needed, so it doesn't run into the pond.

Some ants want protein or fat instead of sugar. You can dip a stick in peanut butter (unsweetened, of course) and see if they swarm it.
If so, mix the borax with peanut butter instead of sugar. Or mix with both and wipe out every kind of ant.

Diatomaceous earth is supposed to kill ants. I haven't tried it, but it certainly kills other bugs.

Corn meal is also mentioned as an ant-killer, but when I did an Internet search, too many folks said it didn't work. Still, a few years ago I scattered corn meal around an active ant nest, and the ants vanished. [In any case, I don't know how corn meal would work in proximity to your pond water.]

I was going to suggest diatomaceous earth as well - we bought ours at Menards (big box store here in the midwest) and it's food grade... safe enough for you to eat, so it won't poison anything else. It kills bugs by dehydrating them. We use it to control the slugs that devour our hostas but I've heard it works great for ants as well.

So I have to sprinkle the Diatomacious earth right on the ants or nests under the rocks? Will they just go around it and build new nests? If it gets into the pond will it cloud up the water or harm the fish if they take some in?

I would rather kill these things off than scare them off. I am not sure how to get the borax mix under the rocks. I hate moving these rocks, the ants swarm. I have no way to protect it from rain. If it is left out near the rocks will it harm anything else that might eat it?

Would it harm the fish in any way if I got those kitchen type ant baits and set them out behind the rocks so maybe the ants would carry that back to the nests? I never really see ant trails but the ants are tiny, they must go out at times to get food, right?

The diatomaceous earth kills them by slicing their bodies when they crawl through it - sounds gross, I know. But seriously - look at your arms! Like I said, you can actually eat the stuff - it has some health properties that escape me right now - so I doubt it could harm your fish. Borax or ant poison would worry me around the pond. You could also try dumping boiling water on them - I've done that when I uncover nests of biting ants in my flower beds and I don't want to apply anything poisonous. Again, sounds cruel, I know... but LOOK AT YOUR ARMS!

Out of curiosity, are there ants anywhere else in your yard? Or just around the pond?

There have been ants elsewhere in the yard, but these seem mostly under rocks. I have never had any that bit before. But I do have a raised bed that I think they have gotten under those rocks as well. I just hate to move the rocks, plus I am afraid they will just keep moving and invading the areas around the pond instead of getting rid of them. It also increases the chances I am going to get swarmed and bit as I move rocks.

I don't know if my approach is safe, since I don't know your pond setup. You wouldn't want to get poison in the pond, but if there are areas near but not directly on top of the ants that couldn't be washed into the pond then fire ant poison should work. The problem is that it will take several weeks.

The critical object of these poisons is to be a bait that the worker ants will take back to the queen. When the queen is dead, the whole group will die too. If you just disturb the ants, then they will just move a little and you could still be in trouble either still with the pond or with other features in your yard. Dead and gone is better. Get the poison. Choose a day that is sunny and warm. You could throw a couple of potato chips or something on the ground to see if the ants are foraging.if you don't see ants on the potato chips within a half hour or so, choose another day. If the poison bait gets damp as it likely would at night, the ants probably wouldn't want to eat it or take it to the nest the next day. I guess it takes three weeks or so for the queen to die.

Wish I had seen your reply a couple of hours ago, I just got back from buying the diatomaceous earth, lol. I will sprinkle that around the area outside of the rocks first and then move a rock and sprinkle under one rock at a time. At least if they scurry out from under the rock they will still run into it if I sprinkle the grass around the rocks first. If they run onto the liner and around the pond some may still escape but at I am going to try this first since I already have it. It says not to contaminate water or food stuffs or breath it in, but it does not say it is dangerous to fish, and only eye irritation to humans and animals. And even a day of exposure to sand at the beach will do that. :) It took WEEKS for those bites to go away.

Well, It has been raining for 2 days so hard to know how well the diatomaceous earth is working. But when I was lifting the rocks to put it down, I pulled back the pond liner a little and it looks like they are under the liner, also. So I am a little afraid I will never be able to get rid of them. Anyone know where I can purchase a pet anteater?

I am going to try putting the bait in used water bottles so my animals can't get to it. I have an ant problem in the flower beds and under the oak tree where the fairy garden is. They do not build mounds but they are fire ants for sure. 2 stings on the knees yesterday.

I believe that fire ants all build mounded soil exits but there are apparently other ants that bite or sting. In any case, you should be sure that you are placing poison near the ants that are biting you and not just any old ants. Regular ants (all ants) are territorial and they will fight off fire ants etc. that are the invaders. The regular ants are your friends.

Any time it rains, you need to reapply the diatomaceous earth - especially heavy rain. We see lots more ants after heavy rains - they must get washed out it their underground tunnels. I hope it helps!