I change my tigers' substrate every 6-8 weeks. My guys consistently defecate in their water dish, so I have to change that daily, but they don't foul the substrate. Eco-Earth seems pretty resistant to mold, too, so I can go a while between changes.
Mealworms are not a good staple food. Gut-loaded crickets are good, roaches better (more meat, less chitin). Nightcrawlers are probably the best all-round feeder.
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Do you see your tigers much or mostly hide?
I think they do not hide as much as most salamnders?