MTS should not have much effect on ramshorns, providing you feed enough. MTS tend to remain in the substrate, except when they come up to the surface to let their babies out, whereas Ramshorns feed everywhere.
They like plants, so you might want to give them some cheap plants to graze over. They eat dead plant matter, not live, but like to graze the biofilm on plants. They don't reproduce as quickly as bladder snails do though, so you might want to try bladder snails too, as an additional source.
Bladder snails are often called pond snails but they are smaller, move much faster and often show up uninvited on plants too.
Nerites are the ones that need salt water for their eggs to hatch.. but they do fine in fresh for daily living.