Calcium dusts just don't stick to mealworms like they do to crix. Since I feed mealworms only to my colony, I add the calcium to the bottom of the feeding dish. This way they lick at it or get a little bit in there mouth when lunging for the food. You can add miner-all I in the dish for added d3. Miner-all has safe levels of d3. I'm switching to a new method though. I'm not to sure how many people are familiar with the new t-rex line of foods. Well, actually they were developed by Allen Repashy (crested gecko fame) and distributed by t-rex. Anyway, there is a leopard gecko blend that is designed to dust on crix. I asked Allen if it would be ok to use in my feeder dish. He suggested using the Gutload formula instead, it can double as a supplement for the leo and act as food for the mealies. I'm giving it a go with some of my groups. If you are interested in learning more about the Sandfire Superfoods you can check out there forum at the link.
Bill
Superfoods forum
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Bill DiFabio
Azteclizard.com
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