At the moment I only have very tiny pond snails in my tank, which I think may be too small for the assassins to consume. I have some sinking wafers which seems to make the assassins wake up and start cruising about, but they are always grabbed and whisked away by my shrimps, so the assassins can't ever reach them. How long can the snails go without food before they perish?
They'll scavenge whatever they can, and happily. I put 6 in my 65l to get rid of the pest snails, which they did nice and quick. They then bred, and I ended up with about 40 of them before I sold them. I didn't feed them anything special, and there was obviously enough food in there for that many to survive. They were also sharing at first with amano shrimps, then I swapped the amanos with the cherries which were in my smaller tank, so there was always enough food for fish, shrimp and 40+ snails.