Please don't add salt to your tank.
I've also seen a shot glass or small clean drinking glass in the tank with an algae wafer inside. The snails will be more visible on the glass, and should accumulate in the cup. I'm sure some shrimp & fish will nibble in the dark, but you should see at least some snails in there as well. A glass bottle may work, but I'd be worried you'd end up catching shrimp or fish & not be able to get them out.
I've also seen a shot glass or small clean drinking glass in the tank with an algae wafer inside. The snails will be more visible on the glass, and should accumulate in the cup. I'm sure some shrimp & fish will nibble in the dark, but you should see at least some snails in there as well. A glass bottle may work, but I'd be worried you'd end up catching shrimp or fish & not be able to get them out.
