That whole idea that sand will kill your fish is just another example of bad information being passed around the web. While an extremely large amount might, the minute it hits oxygenated water, it loses its toxicity to fish.
That said, I don't even vac my sand. My tanks are planted, and it's too big of a pain to try and do. Before I had planted tanks, I'd vac it just like sand. Run the vac down to the bottom, lift up, repeat until done.
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