I recommend keep them indoors, like gold fish. The water can be kept cleaner with regular changes, filters and oxygenated with aeration, and you can monitor their health better. They can be fed brine shrimp or you can use a pair of forceps to move a small piece of beef slowly in front of them. Their diet should be complemented with calcium. You can coat a piece of raw beef with calcium powder so they can ingest whatever amount they can ingest. That is better than nothing. They are sometimes susceptible to fungal skin diseases. You can treat that with a drop of mercurochrome in the water or you can prevent fungal disease with a copper penny (not the tin pennies that are made recently) put in the water.

You can also monitor and regulate water temperature indoors. If it gets above 90 degrees, you can put ice cubes in the tank if they are not kept in an air conditioned room. During winter, you can keep them from freezing weather indoors.

I would recommend smaller worms that wiggle and not cutting them. The debris could get in the water and reduce the oxygen and make it smell bad.

I bought two "water dogs" from petco the other day. I set them up outside in a 2x4x2.5 (in feet) Rubbermaid tub, there's also a goldfish with them. There's no gravel but they do have rocks, a rock cave big enough for both of them to hide in and live plants. It's in the shade most of the day but it can reach 80 degrees where I live but I leave the top half off and the water stays cool. I feed them chopped Canadian earth worms but I'm not sure if they are eating them, or if the goldfish is. Should I bring them indoors and put them in a 20gal tank until I know they are eating, also if my setup is incorrect is a 20gal tank big enough for both of them, they're about 5 inches long