I do not suggest adding a fish to that can grow to over a foot into a tank to take care of snails. Especially not into an 8g aquarium.
My best suggestion is spot removal. Also, feed less. If there is less excess food, there will be fewer snails. you can try putting down a slice of blanched zucchini and picking it up once it becomes snail-filled. That helps take out bigger bunches of them. By continually doing those this, you will definitely be able to help keep the numbers down, or they may just all disappear.
Also, keep in mind, they won't hurt anything. I just leave pest snails alone. they are kinda cute, and just durtle about the tank anyways.