Thanks. I have three assassin snails in there and watched one slide right on by a group of these snails, lol I was like that the heck bud. In my sons 20 gallon tank there are at least 100 of them. We have three assassins in there, a dojo loach, snail trap and lettuce to pull them out yet they just keep coming back.
The assassins should get to grips with them, they may be feeding under the substrait and your only seeing them when the surface to breed or the snails are a little small eather way they should sort them
I believe that they aren’t necessarily a bad “nuisance” to have. They are the only pest snail, as far as I’m aware, that won’t harm living plants and they’re a sign of a healthy ecosystem.
Getting rid of them is difficult though. I follow Rachel O’Leary on YouTube and she just includes reducing pest snail population in her weekly maintenance in her tanks. Check out this video if you haven’t seen it already for some tips:
Dojo don't generally mess with snails in my experience, other types of loaches will but also get too large for a 20 gallon. Kuhli loaches are a good one, they will rip them out of their shells, just have to crush a couple for them to get them on the taste of snail, and they are good in a 20 gallon.
I like ramshorns if they weren't such food opportunists.
Put in a piece of blanched zucchini, if you can, elastic band it to something that will keep it sunk like the photo below. The snails will congregate on it if you leave it overnight for a day or so. Then just lift it out and dispose. Ramshorns will populate more if you are overfeeding, feed less... less snails. Personally I have a good balance in my tank and like them as they do clean algae on the plants.