If tarantulas can go without food for a long period of time. Though this is not recommended and they probably would not like that. You should feed your tarantula 2 crickets every other day. Never feed your tarantula a prey idiom more then half the size of the tarantula.
The main food tarantula keepers use today are crickets. Crickets are a good food source for them and relatively easy to keep.
Keep crickets in a container with a damp substrate for adults if your breeding them. For pinheads you can just use paper towels for the substrate. They like to hide in it too. The damp substrate for adults will help in egg laying. I'll talk about eggs later on. You should also keep egg cartons or paper towels for them to hide in. They hide because if there is no proper food provided for them they can be carnivorous!
For food you should give them gut load, some crushed dog food, and some romaine lettuce. Remember to keep them in the container with the food for 24 hours before feeding them to your tarantula. For water keep a shallow water dish in. You can use a slice of potato for a water source, but I think it grows bacteria quickly.
If you are breeding crickets, because you have more then two tarantulas keep the temperature up by using a light and misting the container. This will aid in egg laying. Also keep the substrate moist. Female crickets can lay up to 500 eggs. So expect a lot pinheads. Remove all the pinheads you can. Put them into another container. When the pinheads are old enough you can put them into your main colony.
Another good idea for spiderlings is to freeze a cricket and then feed it to your tarantula. This is a good idea because some spiderlings are afraid of live ones, some can't catch them, and you can feed large frozen cricket to your tarantula and you don't have to deal with pinheads.
You should feed your tarantulas different food once and a while. Some other food can be meal worms, not very good in nutrition, remember to refrigerate them to slow down there process of becoming adults. Grasshoppers are good. If your tarantula is big enough, you can feed it an occasional pinkie mouse or if it is very big you can feed it a fuzzy mouse. Other insects about half of the tarantulas size are good. Just make sure they don't have pesticides. You can also feed them other smaller tarantulas, but why would you do that? I don't.
Tarantulas don't need vitamins just make sure there food is nutritious.
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