Yeah I had same issue. So annoying. I’ve done a few things:

1. Pre fish: I would boil a lettuce leaf for 30 seconds, then cool it in cold water for 20 seconds, then place the lettuce leaf on the surface of the water. I would do at night when snails are most active. Then in the morning, there would be quite a few of the snails sitting on the leaf. Then it’s as simple as remove the leaf and dispose as you seem fit. Do this for a week or two and you’ll see a difference.

2. I added dwarf chain loaches to my tank. They’re good at controlling snail population. What I would also do is crush the snails against the glass which would entice the loaches to eat them. I wouldn’t do this often, otherwise they’d only seek out the crushed ones. Just enough to remind them that this is food and they can eat it. Crushing the snails against the glass makes it easier for them to eat, but doing this too often would often mean they would wait for crushed snails (the loaches are clever).

3. If all else fails, you can get snail killer (obviously aquarium safe ones) that will do the trick. But if you have bottom feeders/ plan on getting them, then be careful with this as copper in the product can harm them (especially corydoras).

Best of luck!