From time to time you may experience problems with your snails. Very little is known about what these illnesses are, what causes them, and even less is known about treatments. Unfortunately it seems more time is spent on increasingly more ingenious ways to kill them.
Because of this, the following information is a mix of whatever research is possible and available, theory and hypothesis, logical thinking and the result of various discussions with a large group of snail owners. It is with the help of the community at large, that these problems can at least be documented. Where possible I have tried to link to example incidents.
Hopefully, we can find some effective solutions to the majority of these problems but for now I'm afraid you'll have to be content with various suggestions and discussion.
General Care Routine Notes
The general care for a sick snail is really just common sense.
Because so little is known about the effects of various illnesses, and coupled with the fact that in most of these problems we need to monitor their progress, I would suggest isolating the ill ones. This gives you a way to monitor food and calcium intake by examining their faeces, something which would be impossible were you to continue keeping them with others. Obviously for certain problems this may not be applicable or appropriate but the practice is a sound one for most problems not least because you can hopefully stop any contagious problems in their tracks. Ideally it is best to keep them individually for monitoring, especially if the problem is related to eating or the case requires faeces as a means of monitoring progress or regress.
For problems that are pest related I would suggest keeping your snails in very simple conditions to minimise potential hiding places for pests and so you can examine faeces better. It also makes the job of care much simpler and less time-consuming, allowing you to keep on top of the problems more easily.
Perhaps the most ideal tanks are tupperware tubs with holes punched in the lid for small snails and the larger pet-pal style plastic tanks for larger snails, leading to cheap storage boxes for particularly large snails. Your hospital tanks really need to be affordable and easy to maintain. You don't want to be tackling these problems with lots of glass tanks!
If you are aiming to remove the substrate but still want an alternative to the tank floor itself, you could try some capilliary matting or simple jay-cloths, soaked in water. You can still supply a hiding place in the form of a plastic plant pot. Sphagnum moss is a clean alternative to soil, naturally anti-septic, and easy to clean.
However, for problems that are not pest related this may not be the recommended course of action unless you deem it particularly relevant or necessary. This is because of evidence that snails require living bacteria in the soil for good health. Removal of this for long periods can bring about ill-health and ultimately death. (The Life of Achatinidae in London, Presidential address, R. H. Nisbet, Proc. malac. Soc. Lond. (1974) 41, 171). Really, with snails taking time to adjust to new environments this isn't a bad thing, as you want the snail to feel as comfortable as possible. Discretion is needed.
It could well be the case that you will be supplying small quantities of many foods to the snails. To make this easier I use plastic bottle tops as tiny feeding dishes.
Documenting The Problem
Keeping notes on the condition of your ill snails would be a great help to us all because they will hopefully lead, at best, to patterns and scales that match other accounts. At the very least, they can help you spot the symptoms in your other snails earlier, give you a benchmark to work against and an inventory of what has already been tried.
Taking the most instructional photographs you possibly can to help document the problem is a great idea for the reasons stated above but also to bring more visual evidence into the arena. Comparison shots for particularly obscure observations is definitely recommended.