Snails need their habitat to be fairly clean but not to clean because that can be very detrimental to their health and even fatal. They can quickly become 'sick' in unsuitable conditions though, like moldy food in their house, overcrowding, poor ventilation, to high/low humidity or temperature. It's not hard to clean their house but it should be done every week to clean the slime and feces of their glass walls. They also need some basic daily maintenance(cleaning water dish, taking out spoiled food), just like any other pet.
Most things can be cleaned in just warm water with a tooth brush that hasn't been used for any other purpose. Sometimes it's useful to use a small amount of vinegar. It's fantastic for cleaning the glass of their tank. Always wash thoroughly and at least 3 times to make sure you have all the vinegar off. Never clean their food or water dish with vinegar though. Never use diluted bleach instead of vinegar! Yes, it kills the "germs" but it can also kill your snails. Vinegar takes off stubborn slime and makes their house smell fresh and clean. Of course, you should never be able to smell it after you get done rinsing!
Cleaning their tank in the kitchen sink with the spray hose is the easiest way but you may need to spray out the remaining substrate with the garden hose first. I clean the tank as follows: I take everything out except the substrate, put the substrate into bag and freeze, set tank in the sink on its side, rinse with warm water, scrub with toothbrush, rinse again, scrub with diluted vinegar and toothbrush to get stubborn slime off, rinse again, feel sides to make sure I didn't miss any slime spots, rinse again throughly, try to get out all the water and leave to air dry while I get new substrate(garden soil).
If possible, it's a good idea to have two water dishes so you can switch which one is in their house daily and let the other dry completely for several hours for the simple reason that it will help them last longer.
+ Take out all old food nightly that is spoiled or moldy(like cucumber after two days) leaving all food like old lettuce and carrots. Replace with fresh, washed food of all kinds not just the stuff you took out. (feed them like they don't have any food)
+ Clean their water dish in warm water, allow it to dry and fill with about a tablespoon of water.
+ Rinse off their cuttlebone and change/rinse any other calcium source.
+ Check for any eggs and freeze them.
+ Change their substrate and freeze.
+ Clean their entire house, scrub out their tank in the sink with warm water and vinegar using a toothbrush.
+ Clean all their decorations like plastic pots, hiding caves or bird ladders. Try to replace these every few months.
+ Change their cuttlebone for a new piece, about twice a month.
+ Give them a bath when needed or about every 10 days.
Every few months:
+ Replace food and water dish.
+ Between 6-8 months you need to replace their fluorescent bulb if you have one.
+ Replace old decorations like bird ladders or plastic pots.
Little white bugs:
The little white bugs most people see are actually springtails. Springtails are minute, wingless insects about 1/16 to 1/8 inch (1 to 2 mm) long. They can be a variety of colors including white, gray, red, orange, yellow, metallic green and lavender. They get their name from the ability to catapult themselves (leap) through the air three to four inches by means of a taillike mechanism (furcula) tucked under the abdomen. When disturbed, this appendage functions as a spring, propelling them into the air away from the danger source. They're actually harmless and eat decaying plant or animal matter and thrive in the damp substrate. Even though they're harmless, you need to get rid of them if there's hundreds of them because several of the conditions springtails thrive in are detrimental to snails like a waterlogged, old substrate with old, rotting food matter and poor ventilation. If you clean their house as described above you should rarely have a major problem with them.
If you see hundreds of them in your snails' house then you'll need to check your cleaning practices and ventilation. I have found the above cleaning routine to be the best solution for preventing major springtail population explosions. Also make sure your not keeping their substrate to wet and that it isn't waterlogged (has puddles), because that's bad for snails and encourages springtails.
After that, it's best to completely clean their house if there's a lot of them. Move the snails to a spare tank or container with a fresh piece of lettuce. Take out all their food stuffs and feed them to the garbage can. Then take out all their decorations and dishes so your left with just the substrate. Thoroughly clean their accessories with warm water and a toothbrush replacing any that are several months old if possible. Now you need to take out the substrate and freeze it. Then should now be left with a bare tank. Cleaning it at the kitchen sink with the spray hose is easiest. Using warm water, a small amount of vinegar and a toothbrush, thoroughly scrub out their tank. Rinse 3 times and let dry. Fill with new damped substrate and replace their decorations and dishes. Get fresh food for them and give them a bath before returning them to their home.
Try to give them fresh food stuffs daily and take out all the their old food that is rotten. For example, cucumber and fruit can(and should) be in their house for about two days and then must be remove because they spoil. It's best to leave leafy food and things like carrots in their house for two or three days because they eat old food too, not just fresh. This doesn't mean that you should only feed them every other day though because they need fresh food everyday also. Not just fresh food of whatever you took out either - you should pretend they don't have any food and feed them everything you would if they really didn't.
A note on their substrate:
Snails must have access to fresh, biologically active garden soil that's free of any chemicals even if it's just a small handful in their house. If you can not replace this garden soil every week it is better to keep their old soil and clean their house like usual except instead of freezing the soil, very carefully go through it to check for eggs and then put back in their house till next week when you can change it. The main reason you need to clean their house every week is so you can get the slime and feces off the glass.