I'd like to trade 5 small pink rams for one young assassin snail.
The pink rams will be just under breeding size, so if you want to separate them and not have baby snails, you can. If you want a steady population, put them in any tank and let them scrounge for food. Any tank with live plants will give them enough to live happily without a population explosion. If you want to breed them, give them plenty of food and they'll grow faster and be breeding before you know it.
What I want in trade is just one assassin snail. Even trade. I pay to ship my rams to you, you pay to ship your assassin to me.