Amdro bait loses potency quickly when opened.
Dust is your best choice to kill fire ants.
The more rain we have the more you see them as they come up from underground. It is a slow process to kill off a large mound as they have multiple queens and if one survives the mound moves and survives.

I use Ortho Fire Ant Killer. I have had the same container for years. Yesterday I treated a big mound. It appears deserted today. It doesn't take much; maybe a half teaspoon. It works for me.

Relatively new to reading all the wonderful posts....

I also use Ortho, and mine too is a few seasons old. Kicks fire ant butt just like their commercials claim. When they get in my garden I soak the mound with Spinosad. Knocks them out in just over 24 hours.

If you use Ortho dust it doesn't require to be watered in.
If you use the granules it is the same thing as The Othro Max Bug B Gone and much cheaper if you buy the generic bag then the one labeled for Fire Ants. Always read the ingredients. Each company has their propriatary chemicals and use them in most of their products. Anything that is a specialty product will cost more even though it is the exact same thing

Use a fresh product not one from a year ago.
Never disturb the nest.
Apply product when ants are more active- early in the morning or in the evening.
In this case, more is not better.
Sprinkle product as you would salt or pepper.
Do not apply product directly into the hole.
Sprinkle around the mound and a little farther out.
Follow the directions on the back of the container.
The directions are there for a reason.
Starryrider is an expert in this field.
Listen to her advice.

Here is info from UF:
Ineffective home remedies include:

soap solutions and wood ashes soaked into a mound, which supposedly remove the wax layer that protects an ant's body;
applying grits to fire ant mounds in an attempt to get ants to eat the grits, which will then supposedly swell inside them and explode the ants (recall that ants can only ingest liquids, so they do not even eat grits); and,
shoveling mounds together in an attempt to have different colonies fight and kill each other (this is not effective with either single or multiple-queen colonies).

Here is a link that might be useful: Fire Ants

I'm a native and Ortho is the best. In my veggies, I use Saver Diatomaceus Earth. It has a bait in it.

Actually any dust listed for fire ants works equally well. Ortho dust requires more then Spectracide or Bayer. So it isn't your best buy. I don't recommend granules for fire ants because they need to be watered in and you end up killing fewer queens then if you allow the ants to carry the poison in on their bodies.

In my vegetable garden I use Orange oil
6 oz. orange oil
1 tbsp blackstrap molasses
a squeeze of liquid dish soap
Add to a gallon jug and fill with water.
Soak the mound preferably when the ants are not foraging
it works every time and they don't come back.

You just think they don't come back!
Ants feed on oranges and molasses.
Ants are a common pest of citrus.
Soap kills soft bodied insects and ants have a hard shell.

From UF:
The ideal bait contains a slow-acting, non-repellent toxicant that is incorporated into a preferred food substrate. There are many types of baits on the market. Some baits contain:

Insect growth regulators that primarily impact brood production and development (Extinguish, Award, Distance, etc.)

Metabolic inhibitors that primarily kill the foraging workers, the brood and queen (Amdro, Combat, etc.)

Here is a link that might be useful: About Ants

Well I appreciate all of these suggestions, but frankly am even more confused. I guess I'll go to the store and buy fresh fire ant killer. I did try that home remedy of sprinkling grits around, so that doesn't work either. Actually, the bag of outdated stuff I had looked like it had grits in it, I wonder if that's what they use as a carrier? All the things I tried looked like they killed some of the ants and even specific mounds, but the survivors just moved over and started building new mounds within a couple of days. Sevin really works well on contact but it doesn't get to the queen or the ones down inside the mound.