Don't order too many to start- a couple of pounds maximum. They will reproduce eventually to fill the space. More importantly if you make any mistakes and kill off a large number you won't have wasted too much money. You're best adding food really slowly, seeing how much your worms can take. Get to know the biology of your system, and when you know how to look after them well, then buy more if you find you need to get rid of more waste. In general- 1lb of worms is happy in one square foot of surface area.

I agree with the first recommendation: 1-2 lbs. of red wigglers. The discussion below might also be helpful.

Here is a link that might be useful: How many worms to purchase for your home bin

Your container will accommodate a lot of worms, but you probably ought to base the amount of worms on the amount of food you will provide, too. How much food will you be giving them? A high density of worms in an established bin will work fine (and even best if managed well) if you have lots of food. If you have little food for them, like if you eat more meat than veges or get most of your veges frozen or canned (no or few scraps), then you don't want too many worms. In that case a pound will do you. As mentioned, the worms will multiply. It's easier to learn how to manage a bin with smaller numbers so that when you have higher numbers you are ready for them.

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