I started with 1,500 mealworms when i started.. depending on the temperature and what you put them in you will get different growth rates ..
I have gotten the best growth rates using oatmeal( with some multi grain baby cerial). I got the slowest rates with fine meals. Right now i am actually using rolled oats for horses ( super cheap.. although oatmeal is cheap anyways) which i blended a little to open the husks a little more.
I use paper towels on top of the meal for the beatles to hide under and also to lay their eggs on.
I never really pay attention to the temperature for them, but my fiance likes to keep the house at a chilly 65degrees .. although since they are in the laundry room in the summer i am sure it gets up to 80 degrees.
I use potatoe for the veggie, you can really use any type of veggie or fruit as a water source that is fleshy. For a while i used orange fleshed squash ( pumpkin ) since it was in season and sonce i used it to feed other animals. When i prepare any of my veggies i wash them in water that has a drop of Grapefruit Seed Extract in it. Grapefruit Seed Extract is a natural antibacterial that you can get at health food stores or pharmacies ( walmart can order almost anything in if you cant find it anywhere else just to let yah know if you are interested), which i also use to clean our African Greys cage. This keeps the potatoes from molding. They just dry up and the mealworms eat right though the potatoes. i cut mine into slices of 1/4 to 1/2 inch thick and plop them in.
I also just use the little "rubbermaid" plasic 3-4 drawered thingys that you can buy at Walmart or Lowes i use the thin small one that can be basically placed any where in the house and hidden.
Don't worry when after a while your mealworms seem to not move as much ... they will turn into these freaky looking almost chrisalis type brown things .. and Black beatles will hatch from those.. those black beatles do eat so still put veggies in.. when i had mine i also put a bottle cap full of veggie salad i use for my iguana and turtle.. which they ate.. its not neccisary for them though.. the beatles can't climb out of the rubbermaid tub and they only get about max 1/2 an inch or so and i never had one bite me ( i don't even think they can )
Once the beatles die you can pull them out or leave them in which ever you choose. i left some in one tank and my mealworms have eaten at them. Once the beatles died i wondered for a long time if i was going to get babys and almost threw them out until i moved a little of the meal and watched closely and could see it moving just a litte .. then i saw them weeeeeee little worms smaller then pencil lead crawling around on the oatmeal. I was estatic!! now my worms are feeding size .. they look very plump compared to the thin ones i had bought originally so they are very healthy.
If when you do do your worms you actually over compensate and choose to let more then just a few breed you will be rewarded by being able to go everytime you look and find atleast a few that are almost pure white. Those little mealies have just shed their exo skeletons. i know atleast for turtles to many mealies can cause blockages, but the lighter mealies are softer and less likely to cause blockages.