Where do you all buy those silver (metal?) utility shelves that are sturdy enough to keep smallish tanks on? I see fish people use these on pictures on the internet but I'm worried I'll buy a less than sturdy brand that won't hold a tank full of water.

Sam's Club? I think my parents got some from there before and they were definitely the heavy duty type.

Slightly off topic but I'd recommend you put a board down to distribute weight. The shelves aren't solid - just bars down (at least on the shelving I've used) so I feel putting a board on the shelf is best to prevent the weight being distributed wrong and leading to a leak in the tank.