get a tank 10g maybe, fill it with water and get some snails from a local pond and let them breed like for a month, toss in a some plants like maybe grass clippings
these are some common types of pond snails
if your assasin snails would eat trumpet snails you could do the same thing just with more sand in the substrate
trumpet snail
trumpet snails do not need a partner to reproduce
they also give birth to live babies
these are some common types of pond snails
if your assasin snails would eat trumpet snails you could do the same thing just with more sand in the substrate
trumpet snail
trumpet snails do not need a partner to reproduce
they also give birth to live babies