You can leave mealies in 24/7 without a problem. Since calcium really doesn't stick to meal worms I will put some calcium in the bottom of the bowl, so when my leo grabs a meal worm, they also get some calcium as well. The leo will also be able to lick up calcium when they feel they need it as well. I do put a small piece of carrot in the bowl as well so the meal worms have something to feed on. It helps keep them a little more active and moving around...not to mention keeping them a bit more gut loaded for a longer period of time.