Agar does grow bacteria without any added nutrients when in an insect cage. It's a perfect medium for bacteria, and I have seen some nasty stuff growing on it after a few days. That's why I'd only use it for a day or so. But that's the problem--hydration. The poly crystals last for a long time. Agar don't. I'll use Agar for gutloading, feeding, etc, anything where I don't have to leave it in for a long time. For my breeders, I'll use the crystals, and that lasts a long time.
I did have some big die-offs when I used Agar. I kept it in for only a few days, but I lost most of my roaches. I put the agar under the scope, and it was a-swimmming with bacteria, and it stunk like heck. I am planning on using it mixed with greens, as food, but I use the crystals for water.
As far as gelatin goes...
ANIMAL HOOVES???!!??
Don't try and scare people with that. Gelatin is made from Animal Collegen, found in ligaments, connective tissues, tendons, skin and bones. They're gross enough, without hooves. Hooves are mostly Keratin anyway.
Vegans and other groups(PETA) have spread the rumor that it's made of hooves and horns. IT IS a pretty nasty process, and it IS made from pretty nasty stuff(skin, bones, snouts, etc), but Gelitan comes form the bodies of animals slaughtered for FOOD(No, they're not scraping up roadkill...it's amazing the lies PETA spreads).
Gelitan is not "MADE FROM HOOVES!"
Horns and hooves might find their way into the grinder, but that would be incedental, as they are probably contain the LEAST amount of collegen.
Nasty, yes.
Hooves, no.
mixed with fruit flavor, yummy.
Good for vegans--no way in heck
) for this product.