The worm looks like a typical earthworm and as such is harmless.

The snails are likely what are commonly called "bush snails" (see here for photo). They can be difficult to eradicate as they are not attracted to commonly available slug/snail baits. To make matters worse, snails are hermaphrodites -- each has both male and female sex organs. So once two snails mate, BOTH produce eggs. Options that come to mind are as follows:

1. You can try putting a slice of potato in your terr at night and first thing in the morning remove the slice on the chance that some snails will be on or under the slice and can then be destroyed.

2. I noticed in my one terr which has a small snail issue, they seemed to have a fondness for a type of mushroom which had sprouted from a piece of wood in the terr. The mushroom had dried out and I had left it in the tank. Seemed to find snails on it almost every morning. On account of that I left it in there and every morning removed and destroyed any snails I found on it or in the vicinity. Eventually, the buggers managed to eat the dried shroom which left me without my "bait". (Don't know if it was the mushroom itself they were attracted to or some other fungus/bacteria that may have been breaking down the shroom.

3. Some folks have used the CO2 via dry ice method to suffocate terr pests, but I did not find this effective for killing off the snails.

4. Your best bet, unfortunately, is to completely tear down your terr. Remove everything. Then

• Use an ammonia based cleaner like Windex, or chlorine based like Scrubbing Bubbles to clean the tank. Let the cleaner sit for a few minutes before wiping out. Then use damp clean paper towels to wipe down the inside of the terr to remove any remaining residue.
• The media you will put in the tank needs to be sterilized. Moisten it and nuke it in the microwave for 3-5 minutes on High. You may need to do several batches depending upon the amount of media needed. The media should literally be steaming hot throughout (if not needs heated more) so be careful! Steam burns are extremely painful and can even be dangerous.
• The plants will be a tougher issue. Because the snails may have laid their eggs or even be taking refuge themselves in the soil amongst the roots (eggs might also be on moist areas of the plants themselves), you cannot simply put the plants back into the terr unless you practically want to guarantee a return of your snail problem. Remember, all it takes is a couple eggs or one pregnant snail to repopulate your terr. Remove all the media from the plant roots. With plants that readily regrow roots, I'd remove the roots entirely. Make up a 10% bleach solution. Soak the plants for 10mins completely submerged. Thoroughly rinse the plants then soak in clean fresh water for another 10mins to remove any bleach residue you may have missed. With plants that grow readily from cuttings, I would take cuttings at this time. NOTE: Some plants like mosses are very sensitive to chemicals like bleach and may not survive this process but the alternative is snail issues. The plants should now be safe to reintroduce to the terr.

In the future, should you come across a new plant you would like to add to the terr, plan on subjecting the plant to the steps above before putting in the tank -- even if it comes from a reputable grower. Personally, I try to grow new plants in isolation for a few months when I can see if there are any pests to worry about.