It's normal for lots of gnat type things to be flying about this time of year. So perhaps it's coincidence rather than the sea soil.

Vinegar bowls won't help because these definitely aren't the fruit flies that flit around over-ripe fruit.

Thanks jean...
Is there any way to get rid of them?

Most likely they're nothing to worry about. Frankly, gnats happen! :>)

Awesome! ...because if you're not worried about my gnats then I won't either. lol - Thanks very much jean. By the way, do they eat your plant leaves? I have recently planted a climbing rose and it looks like something has been chewing on a couple of new leaves that just opened. There are no aphids, I checked really good. Anyway, just a little curious about that.

Aphids don't chew on leaves. Neither do gnats. Most likely it's a caterpillar. Many moth caterpillars are experts at hiding, coming out at night to eat your plant's leaves.

I second the notion that gnats happen and it's probably just a coincidence that they happened when you bought a bag of soil. Lots of March flies out right now. In California they come out in March but here they don't come out til late April, still called March flies though. Little gnat like things.

In any case, fungus gnats are largely a problem of container plants, not plants in the ground. Containers are watered more often, and container mixes hold water really well, and it's those damp conditions that favor fungus gnats. Not so common in the ground.

I know I the gnats and aphids don't 'chew' on the leaves. - I don't know why I said that. Just now, I imagined a tiny green aphid with great big teeth. Caterpillar huh? Maybe I should check my roses at night with a flashlight. I thought about slugs too. Thanks for your thoughts about the gnats. I didn't know that fungus gnats were just in containers. That's good to know. (Must be those 'March' flies out in 'May')